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117-401: Address space layout randomization ( ASLR ) is a computer security technique involved in preventing exploitation of memory corruption vulnerabilities . In order to prevent an attacker from reliably redirecting code execution to, for example, a particular exploited function in memory, ASLR randomly arranges the address space positions of key data areas of a process , including the base of

234-409: A 32-bit to a 64-bit architecture is a fundamental alteration, as most operating systems must be extensively modified to take advantage of the new architecture, because that software has to manage the actual memory addressing hardware. Other software must also be ported to use the new abilities; older 32-bit software may be supported either by virtue of the 64-bit instruction set being a superset of

351-837: A 64-bit computer architecture generally has integer and addressing registers that are 64 bits wide, allowing direct support for 64-bit data types and addresses. However, a CPU might have external data buses or address buses with different sizes from the registers, even larger (the 32-bit Pentium had a 64-bit data bus, for instance). Processor registers are typically divided into several groups: integer , floating-point , single instruction, multiple data (SIMD), control , and often special registers for address arithmetic which may have various uses and names such as address , index , or base registers . However, in modern designs, these functions are often performed by more general purpose integer registers. In most processors, only integer or address-registers can be used to address data in memory;

468-518: A Linux Test Project testcase to detect this issue. Kernel address space layout randomization (KASLR) enables address space randomization for the Linux kernel image by randomizing where the kernel code is placed at boot time. KASLR was merged into the Linux kernel mainline in kernel version 3.14, released on 30 March 2014. When compiled in, it can be disabled at boot time by specifying nokaslr as one of

585-400: A brute force attack within minutes." (The authors' statement depends on the ability to attack the same application multiple times without any delay. Proper implementations of ASLR, like that included in grsecurity, provide several methods to make such brute force attacks infeasible. One method involves preventing an executable from executing for a configurable amount of time if it has crashed

702-613: A virtual machine of a 16- or 32-bit operating system to run 16-bit applications or use one of the alternatives for NTVDM . Mac OS X 10.4 "Tiger" and Mac OS X 10.5 "Leopard" had only a 32-bit kernel, but they can run 64-bit user-mode code on 64-bit processors. Mac OS X 10.6 "Snow Leopard" had both 32- and 64-bit kernels, and, on most Macs, used the 32-bit kernel even on 64-bit processors. This allowed those Macs to support 64-bit processes while still supporting 32-bit device drivers; although not 64-bit drivers and performance advantages that can come with them. Mac OS X 10.7 "Lion" ran with

819-725: A 16  MiB ( 16 × 1024 bytes ) address space. 32-bit superminicomputers , such as the DEC VAX , became common in the 1970s, and 32-bit microprocessors, such as the Motorola 68000 family and the 32-bit members of the x86 family starting with the Intel 80386 , appeared in the mid-1980s, making 32 bits something of a de facto consensus as a convenient register size. A 32-bit address register meant that 2 addresses, or 4  GB of random-access memory (RAM), could be referenced. When these architectures were devised, 4 GB of memory

936-423: A 32- or 64-bit Java virtual machine with no modification. The lengths and precision of all the built-in types, such as char , short , int , long , float , and double , and the types that can be used as array indices, are specified by the standard and are not dependent on the underlying architecture. Java programs that run on a 64-bit Java virtual machine have access to a larger address space. Speed

1053-609: A 64-bit kernel on more Macs, and OS X 10.8 "Mountain Lion" and later macOS releases only have a 64-bit kernel. On systems with 64-bit processors, both the 32- and 64-bit macOS kernels can run 32-bit user-mode code, and all versions of macOS up to macOS Mojave (10.14) include 32-bit versions of libraries that 32-bit applications would use, so 32-bit user-mode software for macOS will run on those systems. The 32-bit versions of libraries have been removed by Apple in macOS Catalina (10.15). Linux and most other Unix-like operating systems, and

1170-587: A big impact on information security in organizations. Cultural concepts can help different segments of the organization work effectively or work against effectiveness toward information security within an organization. Information security culture is the "...totality of patterns of behavior in an organization that contributes to the protection of information of all kinds." Andersson and Reimers (2014) found that employees often do not see themselves as part of their organization's information security effort and often take actions that impede organizational changes. Indeed,

1287-451: A certain number of times.) On modern 64-bit systems, these numbers typically reach the millions at least. Android, and possibly other systems, implement Library Load Order Randomization , a form of ASLR which randomizes the order in which libraries are loaded. This supplies very little entropy. An approximation of the number of bits of entropy supplied per needed library appears below; this does not yet account for varied library sizes, so

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1404-476: A colleague, which, when listened to by an attacker, could be exploited. Data transmitted across an "open network" allows an attacker to exploit a vulnerability and intercept it via various methods. Unlike malware , direct-access attacks, or other forms of cyber attacks, eavesdropping attacks are unlikely to negatively affect the performance of networks or devices, making them difficult to notice. In fact, "the attacker does not need to have any ongoing connection to

1521-412: A consequence make a Cold boot attack possible, to hardware implementation faults that allow for access or guessing of other values that normally should be inaccessible. In Side-channel attack scenarios, the attacker would gather such information about a system or network to guess its internal state and as a result access the information which is assumed by the victim to be secure. The target information in

1638-780: A driver for a 32-bit PCI device asking the device to DMA data into upper areas of a 64-bit machine's memory could not satisfy requests from the operating system to load data from the device to memory above the 4 gigabyte barrier, because the pointers for those addresses would not fit into the DMA registers of the device. This problem is solved by having the OS take the memory restrictions of the device into account when generating requests to drivers for DMA, or by using an input–output memory management unit (IOMMU). As of August 2023 , 64-bit architectures for which processors are being manufactured include: Most architectures of 64 bits that are derived from

1755-445: A feature of modern computers that allows certain devices, such as external hard drives, graphics cards, or network cards, to access the computer's memory directly." Eavesdropping is the act of surreptitiously listening to a private computer conversation (communication), usually between hosts on a network. It typically occurs when a user connects to a network where traffic is not secured or encrypted and sends sensitive business data to

1872-484: A given process and can have implications for efficient processor cache use. Maintaining a partial 32-bit model is one way to handle this, and is in general reasonably effective. For example, the z/OS operating system takes this approach, requiring program code to reside in 31-bit address spaces (the high order bit is not used in address calculation on the underlying hardware platform) while data objects can optionally reside in 64-bit regions. Not all such applications require

1989-751: A large address space or manipulate 64-bit data items, so these applications do not benefit from these features. x86-based 64-bit systems sometimes lack equivalents of software that is written for 32-bit architectures. The most severe problem in Microsoft Windows is incompatible device drivers for obsolete hardware. Most 32-bit application software can run on a 64-bit operating system in a compatibility mode , also termed an emulation mode, e.g., Microsoft WoW64 Technology for IA-64 and AMD64. The 64-bit Windows Native Mode driver environment runs atop 64-bit NTDLL.DLL , which cannot call 32-bit Win32 subsystem code (often devices whose actual hardware function

2106-480: A malicious code inside a particular HTML or web page. HTML files can carry payloads concealed as benign, inert data in order to defeat content filters . These payloads can be reconstructed on the other side of the filter. When a target user opens the HTML, the malicious code is activated; the web browser then "decodes" the script, which then unleashes the malware onto the target's device. Employee behavior can have

2223-439: A new class of multi-vector, polymorphic cyber threats combine several types of attacks and change form to avoid cybersecurity controls as they spread. Multi-vector polymorphic attacks, as the name describes, are both multi-vectored and polymorphic. Firstly, they are a singular attack that involves multiple methods of attack. In this sense, they are “multi-vectored (i.e. the attack can use multiple means of propagation such as via

2340-578: A per-binary basis. A side-channel attack utilizing branch target buffer was demonstrated to bypass ASLR protection. In 2017, an attack named "ASLR⊕Cache" was demonstrated which could defeat ASLR in a web browser using JavaScript. Computer security Computer security (also cybersecurity , digital security , or information technology (IT) security ) is the protection of computer software , systems and networks from threats that can lead to unauthorized information disclosure, theft or damage to hardware , software , or data , as well as from

2457-521: A problem. 64-bit drivers were not provided for many older devices, which could consequently not be used in 64-bit systems. Driver compatibility was less of a problem with open-source drivers, as 32-bit ones could be modified for 64-bit use. Support for hardware made before early 2007, was problematic for open-source platforms, due to the relatively small number of users. 64-bit versions of Windows cannot run 16-bit software . However, most 32-bit applications will work well. 64-bit users are forced to install

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2574-439: A random base address for the main executable binary and has been in place since April 18, 2004. It provides the same address randomness to the main executable as being used for the shared libraries. The PIE feature cannot be used together with the prelink feature for the same executable. The prelink tool implements randomization at prelink time rather than runtime, because by design prelink aims to handle relocating libraries before

2691-435: A registry entry HKLM\SYSTEM\CurrentControlSet\Control\Session Manager\Memory Management\MoveImages , or by installing Microsoft's Enhanced Mitigation Experience Toolkit . The locations of the heap , stack , Process Environment Block, and Thread Environment Block are also randomized. A security whitepaper from Symantec noted that ASLR in 32-bit Windows Vista may not be as robust as expected, and Microsoft has acknowledged

2808-671: A separate machine filtering network traffic. Firewalls are common amongst machines that are permanently connected to the Internet. Some organizations are turning to big data platforms, such as Apache Hadoop , to extend data accessibility and machine learning to detect advanced persistent threats . 64-bit From the software perspective, 64-bit computing means the use of machine code with 64-bit virtual memory addresses. However, not all 64-bit instruction sets support full 64-bit virtual memory addresses; x86-64 and AArch64 for example, support only 48 bits of virtual address, with

2925-601: A side channel can be challenging to detect due to its low amplitude when combined with other signals Social engineering , in the context of computer security, aims to convince a user to disclose secrets such as passwords, card numbers, etc. or grant physical access by, for example, impersonating a senior executive, bank, a contractor, or a customer. This generally involves exploiting people's trust, and relying on their cognitive biases . A common scam involves emails sent to accounting and finance department personnel, impersonating their CEO and urgently requesting some action. One of

3042-497: A significant entropy reduction in the entropy of libraries after the Linux 5.18 version and identify correlation paths that an attacker could leverage to reduce exploitation complexity significantly. Several mainstream, general-purpose operating systems implement ASLR. Android 4.0 Ice Cream Sandwich provides address space layout randomization (ASLR) to help protect system and third-party applications from exploits due to memory-management issues. Position-independent executable support

3159-405: A single integer register can store the memory address to any location in the computer's physical or virtual memory . Therefore, the total number of addresses to memory is often determined by the width of these registers. The IBM System/360 of the 1960s was an early 32-bit computer; it had 32-bit integer registers, although it only used the low order 24 bits of a word for addresses, resulting in

3276-705: A standard computer user may be able to exploit a vulnerability in the system to gain access to restricted data; or even become root and have full unrestricted access to a system. The severity of attacks can range from attacks simply sending an unsolicited email to a ransomware attack on large amounts of data. Privilege escalation usually starts with social engineering techniques, often phishing . Privilege escalation can be separated into two strategies, horizontal and vertical privilege escalation: Any computational system affects its environment in some form. This effect it has on its environment can range from electromagnetic radiation, to residual effect on RAM cells which as

3393-490: A way of filtering network data between a host or a network and another network, such as the Internet . They can be implemented as software running on the machine, hooking into the network stack (or, in the case of most UNIX -based operating systems such as Linux , built into the operating system kernel ) to provide real-time filtering and blocking. Another implementation is a so-called physical firewall , which consists of

3510-499: A weak form of ASLR by default since the kernel version 2.6.12, released in June 2005. The PaX and Exec Shield patchsets to the Linux kernel provide more complete implementations. The Exec Shield patch for Linux supplies 19 bits of stack entropy on a period of 16 bytes, and 8 bits of mmap base randomization on a period of 1 page of 4096 bytes. This places the stack base in an area 8 MB wide containing 524,288 possible positions, and

3627-535: A weakness in its implementation. Host-based intrusion prevention systems such as WehnTrust and Ozone also offer ASLR for Windows XP and Windows Server 2003 operating systems. WehnTrust is open-source. Complete details of Ozone's implementation are not available. It was noted in February 2012 that ASLR on 32-bit Windows systems prior to Windows 8 can have its effectiveness reduced in low memory situations. A similar effect also had been achieved on Linux in

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3744-447: A wrong password enough consecutive times to cause the victim's account to be locked, or they may overload the capabilities of a machine or network and block all users at once. While a network attack from a single IP address can be blocked by adding a new firewall rule, many forms of distributed denial-of-service (DDoS) attacks are possible, where the attack comes from a large number of points. In this case, defending against these attacks

3861-413: Is a planned extension of KASLR to randomize down to the function level. Microsoft's Windows Vista (released January 2007) and later have ASLR enabled only for executables and dynamic link libraries that are specifically linked to be ASLR-enabled. For compatibility, it is not enabled by default for other applications. Typically, only older software is incompatible and ASLR can be fully enabled by editing

3978-522: Is an abbreviation of "Long, Pointer, 64". Other models are the ILP64 data model in which all three data types are 64 bits wide, and even the SILP64 model where short integers are also 64 bits wide. However, in most cases the modifications required are relatively minor and straightforward, and many well-written programs can simply be recompiled for the new environment with no changes. Another alternative

4095-483: Is emulated in user mode software, like Winprinters). Because 64-bit drivers for most devices were unavailable until early 2007 (Vista x64), using a 64-bit version of Windows was considered a challenge. However, the trend has since moved toward 64-bit computing, more so as memory prices dropped and the use of more than 4 GB of RAM increased. Most manufacturers started to provide both 32-bit and 64-bit drivers for new devices, so unavailability of 64-bit drivers ceased to be

4212-485: Is exactly log 2 ( n ) {\displaystyle \log _{2}\!\left(n\right)} for n intervals attacked. Such decreases are limited due to the amount of data in the stack or heap. The stack, for example, is typically limited to 8  MB and grows to much less; this allows for at most 19 bits , although a more conservative estimate would be around 8– 10 bits corresponding to 4– 16  KB of stack stuffing. The heap on

4329-427: Is more effective when more entropy is present in the random offsets. Entropy is increased by either raising the amount of virtual memory area space over which the randomization occurs or reducing the period over which the randomization occurs. The period is typically implemented as small as possible, so most systems must increase VMA space randomization. To defeat the randomization, attackers must successfully guess

4446-471: Is much more difficult. Such attacks can originate from the zombie computers of a botnet or from a range of other possible techniques, including distributed reflective denial-of-service (DRDoS), where innocent systems are fooled into sending traffic to the victim. With such attacks, the amplification factor makes the attack easier for the attacker because they have to use little bandwidth themselves. To understand why attackers may carry out these attacks, see

4563-518: Is not a perfect subset of information security , therefore does not completely align into the security convergence schema. A vulnerability refers to a flaw in the structure, execution, functioning, or internal oversight of a computer or system that compromises its security. Most of the vulnerabilities that have been discovered are documented in the Common Vulnerabilities and Exposures (CVE) database. An exploitable vulnerability

4680-413: Is not the only factor to consider in comparing 32-bit and 64-bit processors. Applications such as multi-tasking, stress testing, and clustering – for high-performance computing (HPC) – may be more suited to a 64-bit architecture when deployed appropriately. For this reason, 64-bit clusters have been widely deployed in large organizations, such as IBM, HP, and Microsoft. Summary: A common misconception

4797-571: Is now available for 32-bit apps (as are heap memory protections), making 64-bit and 32-bit applications more resistant to attack." As of OS X Mountain Lion 10.8 (released July 2012) and later, the entire system including the kernel as well as kexts and zones are randomly relocated during system boot. ASLR has been introduced in Solaris beginning with Solaris 11.1 (released October 2012). ASLR in Solaris 11.1 can be set system-wide, per zone, or on

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4914-441: Is often written with implicit assumptions about the widths of data types. C code should prefer ( u ) intptr_t instead of long when casting pointers into integer objects. A programming model is a choice made to suit a given compiler, and several can coexist on the same OS. However, the programming model chosen as the primary model for the OS application programming interface (API) typically dominates. Another consideration

5031-504: Is often, but not always, based on 64-bit units of data. For example, although the x86 / x87 architecture has instructions able to load and store 64-bit (and 32-bit) floating-point values in memory, the internal floating-point data and register format is 80 bits wide, while the general-purpose registers are 32 bits wide. In contrast, the 64-bit Alpha family uses a 64-bit floating-point data and register format, and 64-bit integer registers. Many computer instruction sets are designed so that

5148-439: Is one for which at least one working attack or exploit exists. Actors maliciously seeking vulnerabilities are known as threats . Vulnerabilities can be researched, reverse-engineered, hunted, or exploited using automated tools or customized scripts. Various people or parties are vulnerable to cyber attacks; however, different groups are likely to experience different types of attacks more than others. In April 2023,

5265-504: Is protected by standard security measures, these may be bypassed by booting another operating system or tool from a CD-ROM or other bootable media. Disk encryption and the Trusted Platform Module standard are designed to prevent these attacks. Direct service attackers are related in concept to direct memory attacks which allow an attacker to gain direct access to a computer's memory. The attacks "take advantage of

5382-425: Is spear-phishing which leverages personal or organization-specific details to make the attacker appear like a trusted source. Spear-phishing attacks target specific individuals, rather than the broad net cast by phishing attempts. Privilege escalation describes a situation where an attacker with some level of restricted access is able to, without authorization, elevate their privileges or access level. For example,

5499-418: Is that 64-bit architectures are no better than 32-bit architectures unless the computer has more than 4 GB of random-access memory . This is not entirely true: The main disadvantage of 64-bit architectures is that, relative to 32-bit architectures, the same data occupies more space in memory (due to longer pointers and possibly other types, and alignment padding). This increases the memory requirements of

5616-495: Is the IBM AS/400 , software for which is compiled into a virtual instruction set architecture (ISA) called Technology Independent Machine Interface (TIMI); TIMI code is then translated to native machine code by low-level software before being executed. The translation software is all that must be rewritten to move the full OS and all software to a new platform, as when IBM transitioned the native instruction set for AS/400 from

5733-507: Is the LLP64 model, which maintains compatibility with 32-bit code by leaving both int and long as 32-bit. LL refers to the long long integer type, which is at least 64 bits on all platforms, including 32-bit environments. There are also systems with 64-bit processors using an ILP32 data model, with the addition of 64-bit long long integers; this is also used on many platforms with 32-bit processors. This model reduces code size and

5850-400: Is the data model used for device drivers . Drivers make up the majority of the operating system code in most modern operating systems (although many may not be loaded when the operating system is running). Many drivers use pointers heavily to manipulate data, and in some cases have to load pointers of a certain size into the hardware they support for direct memory access (DMA). As an example,

5967-649: The Apple Watch Series 4 and 5. Many 64-bit platforms today use an LP64 model (including Solaris, AIX , HP-UX , Linux, macOS, BSD, and IBM z/OS). Microsoft Windows uses an LLP64 model. The disadvantage of the LP64 model is that storing a long into an int truncates. On the other hand, converting a pointer to a long will "work" in LP64. In the LLP64 model, the reverse is true. These are not problems which affect fully standard-compliant code, but code

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6084-513: The C and C++ toolchains for them, have supported 64-bit processors for many years. Many applications and libraries for those platforms are open-source software , written in C and C++, so that if they are 64-bit-safe, they can be compiled into 64-bit versions. This source-based distribution model, with an emphasis on frequent releases, makes availability of application software for those operating systems less of an issue. In 32-bit programs, pointers and data types such as integers generally have

6201-514: The C standard library and thus one can often assume that β = 1 {\displaystyle \beta \,=1} . However, even for a small number of libraries there are a few bits of entropy gained here; it is thus potentially interesting to combine library load order randomization with VMA address randomization to gain a few extra bits of entropy. These extra bits of entropy will not apply to other mmap() segments, only libraries. Attackers may make use of several methods to reduce

6318-464: The Cray-1 , used registers up to 64 bits wide, and supported 64-bit integer arithmetic, although they did not support 64-bit addressing. In the mid-1980s, Intel i860 development began culminating in a 1989 release; the i860 had 32-bit integer registers and 32-bit addressing, so it was not a fully 64-bit processor, although its graphics unit supported 64-bit integer arithmetic. However, 32 bits remained

6435-963: The Nintendo 64 and the PlayStation 2 had 64-bit microprocessors before their introduction in personal computers. High-end printers, network equipment, and industrial computers also used 64-bit microprocessors, such as the Quantum Effect Devices R5000 . 64-bit computing started to trickle down to the personal computer desktop from 2003 onward, when some models in Apple 's Macintosh lines switched to PowerPC 970 processors (termed G5 by Apple), and Advanced Micro Devices (AMD) released its first 64-bit x86-64 processor. Physical memory eventually caught up with 32 bit limits. In 2023, laptop computers were commonly equipped with 16GB and servers up to 64 GB of memory, greatly exceeding

6552-653: The United Kingdom Department for Science, Innovation & Technology released a report on cyber attacks over the last 12 months. They surveyed 2,263 UK businesses, 1,174 UK registered charities, and 554 education institutions. The research found that "32% of businesses and 24% of charities overall recall any breaches or attacks from the last 12 months." These figures were much higher for "medium businesses (59%), large businesses (69%), and high-income charities with £500,000 or more in annual income (56%)." Yet, although medium or large businesses are more often

6669-468: The executable and the positions of the stack , heap and libraries . The Linux PaX project first coined the term "ASLR", and published the first design and implementation of ASLR in July 2001 as a patch for the Linux kernel . It is seen as a complete implementation, providing a patch for kernel stack randomization since October 2002. The first mainstream operating system to support ASLR by default

6786-483: The integer representation used. With the two most common representations, the range is 0 through 18,446,744,073,709,551,615 (equal to 2 − 1) for representation as an ( unsigned ) binary number , and −9,223,372,036,854,775,808 (−2 ) through 9,223,372,036,854,775,807 (2 − 1) for representation as two's complement . Hence, a processor with 64-bit memory addresses can directly access 2 bytes (16 exabytes or EB) of byte-addressable memory. With no further qualification,

6903-436: The "practice of designing computer systems to achieve security goals." These goals have overlap with the principles of "security by design" explored above, including to "make initial compromise of the system difficult," and to "limit the impact of any compromise." In practice, the role of a security architect would be to ensure the structure of a system reinforces the security of the system, and that new changes are safe and meet

7020-407: The 'attacker motivation' section. A direct-access attack is when an unauthorized user (an attacker) gains physical access to a computer, most likely to directly copy data from it or steal information. Attackers may also compromise security by making operating system modifications, installing software worms , keyloggers , covert listening devices or using wireless microphones. Even when the system

7137-521: The 32-bit instruction set, so that processors that support the 64-bit instruction set can also run code for the 32-bit instruction set, or through software emulation , or by the actual implementation of a 32-bit processor core within the 64-bit processor, as with some Itanium processors from Intel, which included an IA-32 processor core to run 32-bit x86 applications. The operating systems for those 64-bit architectures generally support both 32-bit and 64-bit applications. One significant exception to this

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7254-833: The 32-bit limit of 4 GB ( 4 × 1024 bytes ), allowing room for later expansion and incurring no overhead of translating full 64-bit addresses. The Power ISA v3.0 allows 64 bits for an effective address, mapped to a segmented address with between 65 and 78 bits allowed, for virtual memory, and, for any given processor, up to 60 bits for physical memory. The Oracle SPARC Architecture 2015 allows 64 bits for virtual memory and, for any given processor, between 40 and 56 bits for physical memory. The ARM AArch64 Virtual Memory System Architecture allows 48 bits for virtual memory and, for any given processor, from 32 to 48 bits for physical memory. The DEC Alpha specification requires minimum of 43 bits of virtual memory address space (8 TB) to be supported, and hardware need to check and trap if

7371-655: The 4 GB address capacity of 32 bits. In principle, a 64-bit microprocessor can address 16 EB ( 16 × 1024 = 2 = 18,446,744,073,709,551,616 bytes ) of memory. However, not all instruction sets, and not all processors implementing those instruction sets, support a full 64-bit virtual or physical address space. The x86-64 architecture (as of 2016 ) allows 48 bits for virtual memory and, for any given processor, up to 52 bits for physical memory. These limits allow memory sizes of 256  TB ( 256 × 1024 bytes ) and 4  PB ( 4 × 1024 bytes ), respectively. A PC cannot currently contain 4  petabytes of memory (due to

7488-541: The C library (libc) has, over time, grown in size to exceed this 2 MiB threshold, so instead of being aligned to a (typically) 4 KiB page boundary as before, these libraries are now 2 MiB-aligned: a loss of 9 bits of entropy. For 32-bit Linux, many distributions show no randomization at all in the placement of the libc. For 64-bit Linux, the 28 bits of entropy is reduced to 19 bits. In response, Ubuntu has increased its mmap_rnd_bits setting. Martin Doucha added

7605-768: The CPU branch target predictor buffer (BTB) or memory management unit (MMU) walking page tables. It is not clear if this class of ASLR attack can be mitigated. If they cannot, the benefit of ASLR is reduced or eliminated. In August 2024 a paper was published with an empirical analysis of major desktop platforms, including Linux, macOS, and Windows, by examining the variability in the placement of memory objects across various processes, threads, and system restarts. The results show that while some systems as of 2024, like Linux distributions, provide robust randomization, others, like Windows and macOS, often fail to adequately randomize key areas like executable code and libraries. Moreover, they found

7722-524: The Verizon Data Breach Investigations Report 2020, which examined 3,950 security breaches, discovered 30% of cybersecurity incidents involved internal actors within a company. Research shows information security culture needs to be improved continuously. In "Information Security Culture from Analysis to Change", authors commented, "It's a never-ending process, a cycle of evaluation and change or maintenance." To manage

7839-561: The Web, email and applications." However, they are also multi-staged, meaning that “they can infiltrate networks and move laterally inside the network.” The attacks can be polymorphic, meaning that the cyberattacks used such as viruses, worms or trojans “constantly change (“morph”) making it nearly impossible to detect them using signature-based defences.” Phishing is the attempt of acquiring sensitive information such as usernames, passwords, and credit card details directly from users by deceiving

7956-444: The actual entropy gained is really somewhat higher. Attackers usually need only one library; the math is more complex with multiple libraries, and shown below as well. The case of an attacker using only one library is a simplification of the more complex formula for l = 1 {\displaystyle l=1} . These values tend to be low even for large values of l , most importantly since attackers typically can use only

8073-424: The argument list looks like. Because of the way arguments are typically passed, each format specifier moves closer to the top of the stack frame. Eventually, the return pointer and stack frame pointer can be extracted, revealing the address of a vulnerable library and the address of a known stack frame; this can eliminate library and stack randomization as an obstacle to an attacker. One can also decrease entropy in

8190-444: The attacker has to defeat. The following formulas represent the probability of success for a given set of α attempts on N bits of entropy. In many systems, 2 N {\displaystyle 2^{N}} can be in the thousands or millions. On 32-bit systems, a typical amount of entropy N is 8 bits. For 2004 computer speeds, Shacham and co-workers state "... 16 bits of address randomization can be defeated by

8307-512: The best form of encryption possible for wireless networks is best practice, as well as using HTTPS instead of an unencrypted HTTP . Programs such as Carnivore and NarusInSight have been used by the Federal Bureau of Investigation (FBI) and NSA to eavesdrop on the systems of internet service providers . Even machines that operate as a closed system (i.e., with no contact with the outside world) can be eavesdropped upon by monitoring

8424-421: The disruption or misdirection of the services they provide. The significance of the field stems from the expanded reliance on computer systems , the Internet , and wireless network standards . Its importance is further amplified by the growth of smart devices , including smartphones , televisions , and the various devices that constitute the Internet of things (IoT). Cybersecurity has emerged as one of

8541-407: The dynamic linker has to, which allows the relocation to occur once for many runs of the program. As a result, real address space randomization would defeat the purpose of prelinking. In 2014, Marco-Gisbert and Ripoll disclosed offset2lib technique that weakens Linux ASLR for PIE executables. Linux kernels load PIE executables right after their libraries; as a result, there is a fixed offset between

8658-399: The effectiveness of both 32-bit and 64-bit implementations. Linux filesystems call thp_get_unmapped_area to respond to a file-backed mmap . With a change in 5.18, files greater than 2 MiB are made to return 2 MiB-aligned addresses, so they can be potentially backed by huge pages . (Previously, the increased alignment only applied to Direct Access (DAX) mappings.) In the meantime,

8775-416: The entire computer." Backdoors can be very hard to detect and are usually discovered by someone who has access to the application source code or intimate knowledge of the operating system of the computer. Denial-of-service attacks (DoS) are designed to make a machine or network resource unavailable to its intended users. Attackers can deny service to individual victims, such as by deliberately entering

8892-431: The entropy present in a randomized address space, ranging from simple information leaks to attacking multiple bits of entropy per attack (such as by heap spraying ). There is little that can be done about this. It is possible to leak information about memory layout using format string vulnerabilities . Format string functions such as printf use a variable argument list to do their job; format specifiers describe what

9009-470: The executable and the library functions. If an attacker finds a way to find the address of a function in the executable, the library addresses are also known. They demonstrated an attack that finds the address in fewer than 400 tries. They proposed a new randomize_va_space=3 option to randomize the placement of the executable relative to the library, but it is yet to be incorporated into the upstream as of 2024. The Linux kernel 5.18 released May 2022 reduced

9126-468: The faint electromagnetic transmissions generated by the hardware. TEMPEST is a specification by the NSA referring to these attacks. Malicious software ( malware ) is any software code or computer program "intentionally written to harm a computer system or its users." Once present on a computer, it can leak sensitive details such as personal information, business information and passwords, can give control of

9243-417: The first mainstream operating system to support a strong form of ASLR and to activate it by default. OpenBSD completed its ASLR support in 2008 when it added support for PIE binaries. OpenBSD 4.4's malloc(3) was designed to improve security by taking advantage of ASLR and gap page features implemented as part of OpenBSD's mmap system call , and to detect use-after-free bugs. Released in 2013, OpenBSD 5.3

9360-457: The following sections: Security by design, or alternately secure by design, means that the software has been designed from the ground up to be secure. In this case, security is considered a main feature. The UK government's National Cyber Security Centre separates secure cyber design principles into five sections: These design principles of security by design can include some of the following techniques: Security architecture can be defined as

9477-490: The information security culture, five steps should be taken: pre-evaluation, strategic planning, operative planning, implementation, and post-evaluation. In computer security, a countermeasure is an action, device, procedure or technique that reduces a threat, a vulnerability, or an attack by eliminating or preventing it, by minimizing the harm it can cause, or by discovering and reporting it so that corrective action can be taken. Some common countermeasures are listed in

9594-453: The kernel's boot parameters. There are several side-channel attacks in x86 processors that could leak kernel addresses. In late 2017, kernel page-table isolation (KPTI aka KAISER) was developed to defeat these attacks. However, this method cannot protect against side-channel attacks utilizing collisions in branch predictor structures. As of 2021, finer grained kernel address space layout randomization (or function granular KASLR, FGKASLR)

9711-449: The life-threatening risk of spoofing in the healthcare industry. Tampering describes a malicious modification or alteration of data. It is an intentional but unauthorized act resulting in the modification of a system, components of systems, its intended behavior, or data. So-called Evil Maid attacks and security services planting of surveillance capability into routers are examples. HTML smuggling allows an attacker to "smuggle"

9828-527: The main techniques of social engineering are phishing attacks. In early 2016, the FBI reported that such business email compromise (BEC) scams had cost US businesses more than $ 2 billion in about two years. In May 2016, the Milwaukee Bucks NBA team was the victim of this type of cyber scam with a perpetrator impersonating the team's president Peter Feigin , resulting in the handover of all

9945-542: The mid-1990s, HAL Computer Systems , Sun Microsystems , IBM , Silicon Graphics , and Hewlett-Packard had developed 64-bit architectures for their workstation and server systems. A notable exception to this trend were mainframes from IBM, which then used 32-bit data and 31-bit address sizes; the IBM mainframes did not include 64-bit processors until 2000. During the 1990s, several low-cost 64-bit microprocessors were used in consumer electronics and embedded applications. Notably,

10062-470: The mmap base in an area 1 MB wide containing 256 possible positions. ASLR can be disabled for a specific process by changing its execution domain, using personality(2) . A number of sysctl options control the behavior of mainline ASLR. For example, kernel.randomize_va_space controls what to randomize; the strongest option is 2. vm.mmap_rnd_bits controls how many bits to randomize for mmap . Position-independent executable (PIE) implements

10179-556: The most significant new challenges facing the contemporary world, due to both the complexity of information systems and the societies they support. Security is particularly crucial for systems that govern large-scale systems with far-reaching physical effects, such as power distribution , elections , and finance . Although many aspects of computer security involve digital security, such as electronic passwords and encryption , physical security measures such as metal locks are still used to prevent unauthorized tampering. IT security

10296-473: The nature of backdoors, they are of greater concern to companies and databases as opposed to individuals. Backdoors may be added by an authorized party to allow some legitimate access or by an attacker for malicious reasons. Criminals often use malware to install backdoors, giving them remote administrative access to a system. Once they have access, cybercriminals can "modify files, steal personal information, install unwanted software, and even take control of

10413-409: The norm until the early 1990s, when the continual reductions in the cost of memory led to installations with amounts of RAM approaching 4 GB, and the use of virtual memory spaces exceeding the 4 GB ceiling became desirable for handling certain types of problems. In response, MIPS and DEC developed 64-bit microprocessor architectures, initially for high-end workstation and server machines. By

10530-763: The older 32/48-bit IMPI to the newer 64-bit PowerPC-AS , codenamed Amazon . The IMPI instruction set was quite different from even 32-bit PowerPC, so this transition was even bigger than moving a given instruction set from 32 to 64 bits. On 64-bit hardware with x86-64 architecture (AMD64), most 32-bit operating systems and applications can run with no compatibility issues. While the larger address space of 64-bit architectures makes working with large data sets in applications such as digital video , scientific computing, and large databases easier, there has been considerable debate on whether they or their 32-bit compatibility modes will be faster than comparably priced 32-bit systems for other tasks. A compiled Java program can run on

10647-560: The openness of the Internet. These strategies mostly include phishing , ransomware , water holing and scanning. To secure a computer system, it is important to understand the attacks that can be made against it, and these threats can typically be classified into one of the following categories: A backdoor in a computer system, a cryptosystem , or an algorithm is any secret method of bypassing normal authentication or security controls. These weaknesses may exist for many reasons, including original design or poor configuration. Due to

10764-588: The other hand is limited by the behavior of the memory allocator; in the case of glibc , allocations above 128 KB are created using mmap , limiting attackers to 5 bits of reduction. This is also a limiting factor when brute forcing; although the number of attacks to perform can be reduced, the size of the attacks is increased enough that the behavior could in some circumstances become apparent to intrusion detection systems . ASLR-protected addresses can be leaked by various side channels, removing mitigation utility. Recent attacks have used information leaked by

10881-428: The other types of registers cannot. The size of these registers therefore normally limits the amount of directly addressable memory, even if there are registers, such as floating-point registers, that are wider. Most high performance 32-bit and 64-bit processors (some notable exceptions are older or embedded ARM architecture (ARM) and 32-bit MIPS architecture (MIPS) CPUs) have integrated floating point hardware, which

10998-420: The physical size of the memory chips), but AMD envisioned large servers, shared memory clusters, and other uses of physical address space that might approach this in the foreseeable future. Thus the 52-bit physical address provides ample room for expansion while not incurring the cost of implementing full 64-bit physical addresses. Similarly, the 48-bit virtual address space was designed to provide 65,536 (2 ) times

11115-492: The positions of all areas they wish to attack. For data areas such as stack and heap, where custom code or useful data can be loaded, more than one state can be attacked by using NOP slides for code or repeated copies of data. This allows an attack to succeed if the area is randomized to one of a handful of values. In contrast, code areas such as library base and main executable need to be discovered exactly. Often these areas are mixed, for example stack frames are injected onto

11232-428: The real website. Preying on a victim's trust, phishing can be classified as a form of social engineering . Attackers can use creative ways to gain access to real accounts. A common scam is for attackers to send fake electronic invoices to individuals showing that they recently purchased music, apps, or others, and instructing them to click on a link if the purchases were not authorized. A more strategic type of phishing

11349-416: The remaining 16 bits of the virtual address required to be all zeros (000...) or all ones (111...), and several 64-bit instruction sets support fewer than 64 bits of physical memory address. The term 64-bit also describes a generation of computers in which 64-bit processors are the norm. 64 bits is a word size that defines certain classes of computer architecture, buses, memory, and CPUs and, by extension,

11466-547: The remaining unsupported bits are zero (to support compatibility on future processors). Alpha 21064 supported 43 bits of virtual memory address space (8 TB) and 34 bits of physical memory address space (16 GB). Alpha 21164 supported 43 bits of virtual memory address space (8 TB) and 40 bits of physical memory address space (1 TB). Alpha 21264 supported user-configurable 43 or 48 bits of virtual memory address space (8 TB or 256 TB) and 44 bits of physical memory address space (16 TB). A change from

11583-476: The right foundation to systematically address business, IT and security concerns in an organization. A state of computer security is the conceptual ideal, attained by the use of three processes: threat prevention, detection, and response. These processes are based on various policies and system components, which include the following: Today, computer security consists mainly of preventive measures, like firewalls or an exit procedure . A firewall can be defined as

11700-486: The same length. This is not necessarily true on 64-bit machines. Mixing data types in programming languages such as C and its descendants such as C++ and Objective-C may thus work on 32-bit implementations but not on 64-bit implementations. In many programming environments for C and C-derived languages on 64-bit machines, int variables are still 32 bits wide, but long integers and pointers are 64 bits wide. These are described as having an LP64 data model , which

11817-722: The same research. The test code caused the Mac OS X 10.7.3 system to kernel panic , so it was left unclear about its ASLR behavior in this scenario. Support for ASLR in userland appeared in NetBSD 5.0 (released April 2009), and was enabled by default in NetBSD-current in April 2016. Kernel ASLR support on amd64 was added in NetBSD-current in October 2017, making NetBSD the first BSD system to support KASLR. In 2003, OpenBSD became

11934-432: The security requirements of the organization. Similarly, Techopedia defines security architecture as "a unified security design that addresses the necessities and potential risks involved in a certain scenario or environment. It also specifies when and where to apply security controls. The design process is generally reproducible." The key attributes of security architecture are: Practicing security architecture provides

12051-448: The size of data structures containing pointers, at the cost of a much smaller address space, a good choice for some embedded systems. For instruction sets such as x86 and ARM in which the 64-bit version of the instruction set has more registers than does the 32-bit version, it provides access to the additional registers without the space penalty. It is common in 64-bit RISC machines, explored in x86 as x32 ABI , and has recently been used in

12168-448: The software at all. The attacker can insert the software onto a compromised device, perhaps by direct insertion or perhaps by a virus or other malware, and then come back some time later to retrieve any data that is found or trigger the software to send the data at some determined time." Using a virtual private network (VPN), which encrypts data between two points, is one of the most common forms of protection against eavesdropping. Using

12285-562: The software that runs on them. 64-bit CPUs have been used in supercomputers since the 1970s ( Cray-1 , 1975) and in reduced instruction set computers (RISC) based workstations and servers since the early 1990s. In 2003, 64-bit CPUs were introduced to the mainstream PC market in the form of x86-64 processors and the PowerPC G5 . A 64-bit register can hold any of 2 (over 18 quintillion or 1.8×10 ) different values. The range of integer values that can be stored in 64 bits depends on

12402-476: The stack and a library is returned into. The following variables can be declared: To calculate the probability of an attacker succeeding, a number of attempts α carried out without being interrupted by a signature-based IPS, law enforcement, or other factor must be assumed; in the case of brute forcing, the daemon cannot be restarted. The number of relevant bits and how many are being attacked in each attempt must also be calculated, leaving however many bits

12519-507: The stack or heap. The stack typically must be aligned to 16 bytes, and so this is the smallest possible randomization interval; while the heap must be page-aligned, typically 4096 bytes. When attempting an attack, it is possible to align duplicate attacks with these intervals; a NOP slide may be used with shellcode injection , and the string ' /bin/sh ' can be replaced with ' ////////bin/sh ' for an arbitrary number of slashes when attempting to return to system . The number of bits removed

12636-478: The sysctl vm.randomize_mmap to 1. Support for ASLR appeared in FreeBSD 13.0. It is enabled by default since 13.2. Apple introduced ASLR in iOS 4.3 (released March 2011). KASLR was introduced in iOS 6. The randomized kernel base is 0x01000000 + ((1+0xRR) * 0x00200000) , where 0xRR is a random byte from SHA1 (random data) generated by iBoot (the 2nd-stage iOS Boot Loader). The Linux kernel enabled

12753-423: The system makes related memory-addresses unpredictable from the attackers' point of view. These values have to be guessed, and a mistaken guess is not usually recoverable due to the application crashing. Address space layout randomization is based upon the low chance of an attacker guessing the locations of randomly placed areas. Security is increased by increasing the search space. Thus, address space randomization

12870-677: The system to the attacker, and can corrupt or delete data permanently. Another type of malware is ransomware , which is when "malware installs itself onto a victim's machine, encrypts their files, and then turns around and demands a ransom (usually in Bitcoin ) to return that data to the user." Types of malware include some of the following: Man-in-the-middle attacks (MITM) involve a malicious attacker trying to intercept, surveil or modify communications between two parties by spoofing one or both party's identities and injecting themselves in-between. Types of MITM attacks include: Surfacing in 2017,

12987-428: The team's employees' 2015 W-2 tax forms. Spoofing is an act of pretending to be a valid entity through the falsification of data (such as an IP address or username), in order to gain access to information or resources that one is otherwise unauthorized to obtain. Spoofing is closely related to phishing . There are several types of spoofing, including: In 2018, the cybersecurity firm Trellix published research on

13104-427: The users. Phishing is typically carried out by email spoofing , instant messaging , text message , or on a phone call. They often direct users to enter details at a fake website whose look and feel are almost identical to the legitimate one. The fake website often asks for personal information, such as login details and passwords. This information can then be used to gain access to the individual's real account on

13221-616: The victims, since larger companies have generally improved their security over the last decade, small and midsize businesses (SMBs) have also become increasingly vulnerable as they often "do not have advanced tools to defend the business." SMBs are most likely to be affected by malware, ransomware, phishing, man-in-the-middle attacks , and Denial-of Service (DoS) Attacks. Normal internet users are most likely to be affected by untargeted cyberattacks. These are where attackers indiscriminately target as many devices, services, or users as possible. They do this using techniques that take advantage of

13338-427: Was OpenBSD version 3.4 in 2003, followed by Linux in 2005. Address space randomization hinders some types of security attacks by making it more difficult for an attacker to predict target addresses. For example, attackers trying to execute return-to-libc attacks must locate the code to be executed, while other attackers trying to execute shellcode injected on the stack have to find the stack first. In both cases,

13455-484: Was added in Android 4.1. Android 5.0 dropped non-PIE support and requires all dynamically linked binaries to be position independent. Library load ordering randomization was accepted into the Android open-source project on 26 October 2015, and was included in the Android 7.0 release. DragonFly BSD has an implementation of ASLR based upon OpenBSD's model, added in 2010. It is off by default, and can be enabled by setting

13572-416: Was so far beyond the typical amounts (4 MiB) in installations, that this was considered to be enough headroom for addressing. 4.29 billion addresses were considered an appropriate size to work with for another important reason: 4.29 billion integers are enough to assign unique references to most entities in applications like databases . Some supercomputer architectures of the 1970s and 1980s, such as

13689-529: Was the first mainstream operating system to enable position-independent executables by default on multiple hardware platforms , and OpenBSD 5.7 activated position-independent static binaries (Static-PIE) by default. In Mac OS X Leopard 10.5 (released October 2007), Apple introduced randomization for system libraries. In Mac OS X Lion 10.7 (released July 2011), Apple expanded their implementation to cover all applications, stating "address space layout randomization (ASLR) has been improved for all applications. It

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