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71-412: When the intent is secrecy protection , such as in dealing with classified information , redaction attempts to reduce the document's classification level, possibly yielding an unclassified document. When the intent is privacy protection , it is often called data anonymization . Originally, the term sanitization was applied to printed documents; it has since been extended to apply to computer files and

142-497: A computer a brief window of time to move information from primary volatile storage into non-volatile storage before the batteries are exhausted. Some systems, for example EMC Symmetrix , have integrated batteries that maintain volatile storage for several minutes. Utilities such as hdparm and sar can be used to measure IO performance in Linux. Full disk encryption , volume and virtual disk encryption, andor file/folder encryption

213-552: A document, Redaction Toolkit, Guidelines for the Editing of Exempt Information from Documents Prior to Release , "to provide guidance on the editing of exempt material from information held by public bodies." Secure redacting is more complicated with computer files . Word processing formats may save a revision history of the edited text that still contains the redacted text. In some file formats, unused portions of memory are saved that may still contain fragments of previous versions of

284-702: A drive. When the computer has finished reading the information, the robotic arm will return the medium to its place in the library. Tertiary storage is also known as nearline storage because it is "near to online". The formal distinction between online, nearline, and offline storage is: For example, always-on spinning hard disk drives are online storage, while spinning drives that spin down automatically, such as in massive arrays of idle disks ( MAID ), are nearline storage. Removable media such as tape cartridges that can be automatically loaded, as in tape libraries , are nearline storage, while tape cartridges that must be manually loaded are offline storage. Off-line storage

355-432: A guidance document which provides instructions for redacting PDF files. Printed documents which contain classified or sensitive information frequently contain a great deal of information which is less sensitive. There may be a need to release the less sensitive portions to uncleared personnel. The printed document will consequently be sanitized to obscure or remove the sensitive information. Maps have also been redacted for

426-492: A limited time monopoly on its use, though patent applications are initially secret. Secret societies use secrecy as a way to attract members by creating a sense of importance. Shell companies may be used to launder money from criminal activity, to finance terrorism, or to evade taxes. Registers of beneficial ownership aim at fighting corporate secrecy in that sense. Other laws require organizations to keep certain information secret, such as medical records ( HIPAA in

497-523: A memory in which they store their operating instructions and data. Such computers are more versatile in that they do not need to have their hardware reconfigured for each new program, but can simply be reprogrammed with new in-memory instructions; they also tend to be simpler to design, in that a relatively simple processor may keep state between successive computations to build up complex procedural results. Most modern computers are von Neumann machines. A modern digital computer represents data using

568-476: A sanitization failure caused by unexpected behavior in Microsoft Word's change tracking feature. The two most common mistakes for incorrectly redacting a document are adding an image layer over the sensitive text to obscure it, without removing the underlying text, and setting the background color to match the text color. In both of these cases, the redacted material still exists in the document underneath

639-497: A secret. Also, the other may insist that one answer the question. Nearly 2500 years ago, Sophocles wrote: 'Do nothing secretly; for Time sees and hears all things, and discloses all.'. Gautama Siddhartha said: "Three things cannot long stay hidden: the sun , the moon and the truth .". Computer storage Computer data storage or digital data storage is a technology consisting of computer components and recording media that are used to retain digital data . It

710-574: A source to read instructions from, in order to start the computer. Hence, non-volatile primary storage containing a small startup program ( BIOS ) is used to bootstrap the computer, that is, to read a larger program from non-volatile secondary storage to RAM and start to execute it. A non-volatile technology used for this purpose is called ROM, for read-only memory (the terminology may be somewhat confusing as most ROM types are also capable of random access ). Many types of "ROM" are not literally read only , as updates to them are possible; however it

781-750: A subject of the laws, as is true outside of elections) in selecting their government servants. It is argued that secrecy is impermissible as against the public in the area of elections where the government gets all of its power and taxing authority. In any event, permissible secrecy varies significantly with the context involved. Organizations, ranging from multi-national for profit corporations to nonprofit charities , keep secrets for competitive advantage , to meet legal requirements, or, in some cases, to conceal nefarious behavior. New products under development, unique manufacturing techniques, or simply lists of customers are types of information protected by trade secret laws. Research on corporate secrecy has studied

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852-479: A user with the aid of "redaction" functions in software for editing PDF or other files. Redaction may administratively require marking of the redacted area with the reason that the content is being restricted. US government documents released under the Freedom of Information Act are marked with exemption codes that denote the reason why the content has been withheld. The US National Security Agency (NSA) published

923-465: A wide black pen, followed by photocopying the result—the obscured text may be recoverable from the original. Alternatively opaque "cover up tape" or "redaction tape", opaque, removable adhesive tape in various widths, may be applied before photocopying. This is a simple process with only minor security risks. For example, if the black pen or tape is not wide enough, careful examination of the resulting photocopy may still reveal partial information about

994-747: A word processor. On May 24, 2006, lawyers for the communications service provider AT&T filed a legal brief regarding their cooperation with domestic wiretapping by the NSA. Text on pages 12 to 14 of the PDF document were incorrectly redacted, and the covered text could be retrieved. At the end of 2005, the NSA released a report giving recommendations on how to safely sanitize a Microsoft Word document. Issues such as these make it difficult to reliably implement multilevel security systems, in which computer users of differing security clearances may share documents. The Challenge of Multilevel Security gives an example of

1065-498: Is Joseph Conrad 's short story " The Secret Sharer ". Governments often attempt to conceal information from other governments and the public. These state secrets can include weapon designs, military plans, diplomatic negotiation tactics, and secrets obtained illicitly from others (" intelligence "). Most nations have some form of Official Secrets Act (the Espionage Act in the U.S.) and classify material according to

1136-459: Is data remanence . In some contexts (notably the US NSA, DoD , and related organizations), "sanitization" typically refers to countering the data remanence problem. However, the retention may be a deliberate feature , in the form of an undo buffer, revision history, "trash can", backups , or the like. For example, word processing programs like Microsoft Word will sometimes be used to edit out

1207-550: Is a core function and fundamental component of computers. The central processing unit (CPU) of a computer is what manipulates data by performing computations. In practice, almost all computers use a storage hierarchy , which puts fast but expensive and small storage options close to the CPU and slower but less expensive and larger options further away. Generally, the fast technologies are referred to as "memory", while slower persistent technologies are referred to as "storage". Even

1278-427: Is a form of volatile memory that also requires the stored information to be periodically reread and rewritten, or refreshed , otherwise it would vanish. Static random-access memory is a form of volatile memory similar to DRAM with the exception that it never needs to be refreshed as long as power is applied; it loses its content when the power supply is lost. An uninterruptible power supply (UPS) can be used to give

1349-425: Is a level below secondary storage. Typically, it involves a robotic mechanism which will mount (insert) and dismount removable mass storage media into a storage device according to the system's demands; such data are often copied to secondary storage before use. It is primarily used for archiving rarely accessed information since it is much slower than secondary storage (e.g. 5–60 seconds vs. 1–10 milliseconds). This

1420-410: Is computer data storage on a medium or a device that is not under the control of a processing unit . The medium is recorded, usually in a secondary or tertiary storage device, and then physically removed or disconnected. It must be inserted or connected by a human operator before a computer can access it again. Unlike tertiary storage, it cannot be accessed without human interaction. Off-line storage

1491-609: Is estimable using S.M.A.R.T. diagnostic data that includes the hours of operation and the count of spin-ups, though its reliability is disputed. Flash storage may experience downspiking transfer rates as a result of accumulating errors, which the flash memory controller attempts to correct. The health of optical media can be determined by measuring correctable minor errors , of which high counts signify deteriorating and/or low-quality media. Too many consecutive minor errors can lead to data corruption. Not all vendors and models of optical drives support error scanning. As of 2011 ,

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1562-403: Is not kept secret. Information hiding is a design principle in much software engineering . It is considered easier to verify software reliability if one can be sure that different parts of the program can only access (and therefore depend on) a known limited amount of information. Military secrecy is the concealing of information about martial affairs that is purposely not made available to

1633-416: Is primarily useful for extraordinarily large data stores, accessed without human operators. Typical examples include tape libraries and optical jukeboxes . When a computer needs to read information from the tertiary storage, it will first consult a catalog database to determine which tape or disc contains the information. Next, the computer will instruct a robotic arm to fetch the medium and place it in

1704-713: Is readily available for most storage devices. Hardware memory encryption is available in Intel Architecture, supporting Total Memory Encryption (TME) and page granular memory encryption with multiple keys (MKTME). and in SPARC M7 generation since October 2015. Distinct types of data storage have different points of failure and various methods of predictive failure analysis . Vulnerabilities that can instantly lead to total loss are head crashing on mechanical hard drives and failure of electronic components on flash storage. Impending failure on hard disk drives

1775-491: Is slow and memory must be erased in large portions before it can be re-written. Some embedded systems run programs directly from ROM (or similar), because such programs are rarely changed. Standard computers do not store non-rudimentary programs in ROM, and rather, use large capacities of secondary storage, which is non-volatile as well, and not as costly. Recently, primary storage and secondary storage in some uses refer to what

1846-442: Is the only one directly accessible to the CPU. The CPU continuously reads instructions stored there and executes them as required. Any data actively operated on is also stored there in a uniform manner. Historically, early computers used delay lines , Williams tubes , or rotating magnetic drums as primary storage. By 1954, those unreliable methods were mostly replaced by magnetic-core memory . Core memory remained dominant until

1917-436: Is typically corrected upon detection. A bit or a group of malfunctioning physical bits (the specific defective bit is not always known; group definition depends on the specific storage device) is typically automatically fenced out, taken out of use by the device, and replaced with another functioning equivalent group in the device, where the corrected bit values are restored (if possible). The cyclic redundancy check (CRC) method

1988-505: Is typically measured in milliseconds (thousandths of a second), while the access time per byte for primary storage is measured in nanoseconds (billionths of a second). Thus, secondary storage is significantly slower than primary storage. Rotating optical storage devices, such as CD and DVD drives, have even longer access times. Other examples of secondary storage technologies include USB flash drives , floppy disks , magnetic tape , paper tape , punched cards , and RAM disks . Once

2059-470: Is typically used in communications and storage for error detection . A detected error is then retried. Data compression methods allow in many cases (such as a database) to represent a string of bits by a shorter bit string ("compress") and reconstruct the original string ("decompress") when needed. This utilizes substantially less storage (tens of percent) for many types of data at the cost of more computation (compress and decompress when needed). Analysis of

2130-496: Is used to transfer information since the detached medium can easily be physically transported. Additionally, it is useful for cases of disaster, where, for example, a fire destroys the original data, a medium in a remote location will be unaffected, enabling disaster recovery . Off-line storage increases general information security since it is physically inaccessible from a computer, and data confidentiality or integrity cannot be affected by computer-based attack techniques. Also, if

2201-690: The CPU ( secondary or tertiary storage ), typically hard disk drives , optical disc drives, and other devices slower than RAM but non-volatile (retaining contents when powered down). Historically, memory has, depending on technology, been called central memory , core memory , core storage , drum , main memory , real storage , or internal memory . Meanwhile, slower persistent storage devices have been referred to as secondary storage , external memory , or auxiliary/peripheral storage . Primary storage (also known as main memory , internal memory , or prime memory ), often referred to simply as memory ,

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2272-523: The arithmetic logic unit (ALU). The former controls the flow of data between the CPU and memory, while the latter performs arithmetic and logical operations on data. Without a significant amount of memory, a computer would merely be able to perform fixed operations and immediately output the result. It would have to be reconfigured to change its behavior. This is acceptable for devices such as desk calculators , digital signal processors , and other specialized devices. Von Neumann machines differ in having

2343-417: The binary numeral system . Text, numbers, pictures, audio, and nearly any other form of information can be converted into a string of bits , or binary digits, each of which has a value of 0 or 1. The most common unit of storage is the byte , equal to 8 bits. A piece of information can be handled by any computer or device whose storage space is large enough to accommodate the binary representation of

2414-476: The disk read/write head on HDDs reaches the proper placement and the data, subsequent data on the track are very fast to access. To reduce the seek time and rotational latency, data are transferred to and from disks in large contiguous blocks. Sequential or block access on disks is orders of magnitude faster than random access, and many sophisticated paradigms have been developed to design efficient algorithms based on sequential and block access. Another way to reduce

2485-470: The landmark legal case of United States v. Reynolds , decided by the Supreme Court in 1953. Excessive secrecy is often cited as a source of much human conflict. One may have to lie in order to hold a secret, which might lead to psychological repercussions. The alternative, declining to answer when asked something, may suggest the answer and may therefore not always be suitable for keeping

2556-690: The 1970s, when advances in integrated circuit technology allowed semiconductor memory to become economically competitive. This led to modern random-access memory (RAM). It is small-sized, light, but quite expensive at the same time. The particular types of RAM used for primary storage are volatile , meaning that they lose the information when not powered. Besides storing opened programs, it serves as disk cache and write buffer to improve both reading and writing performance. Operating systems borrow RAM capacity for caching so long as it's not needed by running software. Spare memory can be utilized as RAM drive for temporary high-speed data storage. As shown in

2627-511: The I/O bottleneck is to use multiple disks in parallel to increase the bandwidth between primary and secondary memory. Secondary storage is often formatted according to a file system format, which provides the abstraction necessary to organize data into files and directories , while also providing metadata describing the owner of a certain file, the access time, the access permissions, and other information. Most computer operating systems use

2698-410: The U.S. Freedom of Information Act and sunshine laws . Government officials sometimes leak information they are supposed to keep secret. ( For a recent (2005) example, see Plame affair . ) Secrecy in elections is a growing issue, particularly secrecy of vote counts on computerized vote counting machines. While voting, citizens are acting in a unique sovereign or "owner" capacity (instead of being

2769-422: The U.S.), or financial reports that are under preparation (to limit insider trading ). Europe has particularly strict laws about database privacy. Preservation of secrets is one of the goals of information security . Techniques used include physical security and cryptography . The latter depends on the secrecy of cryptographic keys . Many believe that security technology can be more effective if it itself

2840-502: The US military published a report on the death of Nicola Calipari , an Italian secret agent, at a US military checkpoint in Iraq. The published version of the report was in PDF format, and had been incorrectly redacted by covering sensitive parts with opaque blocks in software. Shortly thereafter, readers discovered that the blocked-out portions could be retrieved by copying and pasting them into

2911-424: The computer to detect errors in coded data and correct them based on mathematical algorithms. Errors generally occur in low probabilities due to random bit value flipping, or "physical bit fatigue", loss of the physical bit in the storage of its ability to maintain a distinguishable value (0 or 1), or due to errors in inter or intra-computer communication. A random bit flip (e.g. due to random radiation )

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2982-524: The concept of virtual memory , allowing the utilization of more primary storage capacity than is physically available in the system. As the primary memory fills up, the system moves the least-used chunks ( pages ) to a swap file or page file on secondary storage, retrieving them later when needed. If a lot of pages are moved to slower secondary storage, the system performance is degraded. The secondary storage, including HDD , ODD and SSD , are usually block-addressable. Tertiary storage or tertiary memory

3053-430: The desired data to primary storage. Secondary storage is non-volatile (retaining data when its power is shut off). Modern computer systems typically have two orders of magnitude more secondary storage than primary storage because secondary storage is less expensive. In modern computers, hard disk drives (HDDs) or solid-state drives (SSDs) are usually used as secondary storage. The access time per byte for HDDs or SSDs

3124-494: The desired location of data. Then it reads or writes the data in the memory cells using the data bus. Additionally, a memory management unit (MMU) is a small device between CPU and RAM recalculating the actual memory address, for example to provide an abstraction of virtual memory or other tasks. As the RAM types used for primary storage are volatile (uninitialized at start up), a computer containing only such storage would not have

3195-400: The diagram, traditionally there are two more sub-layers of the primary storage, besides main large-capacity RAM: Main memory is directly or indirectly connected to the central processing unit via a memory bus . It is actually two buses (not on the diagram): an address bus and a data bus . The CPU firstly sends a number through an address bus, a number called memory address , that indicates

3266-412: The document. Computer (electronic or digital) documents are more difficult to sanitize. In many cases, when information in an information system is modified or erased, some or all of the data remains in storage . This may be an accident of design, where the underlying storage mechanism ( disk , RAM , etc.) still allows information to be read, despite its nominal erasure. The general term for this problem

3337-471: The factors supporting secret organizations. In particular, scholars in economics and management have paid attention to the way firms participating in cartels work together to maintain secrecy and conceal their activities from antitrust authorities. The diversity of the participants (in terms of age and size of the firms) influences their ability to coordinate to avoid being detected. The patent system encourages inventors to publish information in exchange for

3408-411: The family with outsiders or sometimes even within the family. Many "family secrets" are maintained by using a mutually agreed-upon construct (an official family story) when speaking with outside members. Agreement to maintain the secret is often coerced through "shaming" and reference to family honor . The information may even be something as trivial as a recipe . Secrets are sometimes kept to provide

3479-465: The first computer designs, Charles Babbage 's Analytical Engine and Percy Ludgate 's Analytical Machine, clearly distinguished between processing and memory (Babbage stored numbers as rotations of gears, while Ludgate stored numbers as displacements of rods in shuttles). This distinction was extended in the Von Neumann architecture , where the CPU consists of two main parts: The control unit and

3550-477: The former using standard MOSFETs and the latter using floating-gate MOSFETs . In modern computers, primary storage almost exclusively consists of dynamic volatile semiconductor random-access memory (RAM), particularly dynamic random-access memory (DRAM). Since the turn of the century, a type of non-volatile floating-gate semiconductor memory known as flash memory has steadily gained share as off-line storage for home computers. Non-volatile semiconductor memory

3621-582: The general public and hence to any enemy, in order to gain an advantage or to not reveal a weakness, to avoid embarrassment , or to help in propaganda efforts. Most military secrets are tactical in nature, such as the strengths and weaknesses of weapon systems , tactics , training methods, plans, and the number and location of specific weapons. Some secrets involve information in broader areas, such as secure communications, cryptography , intelligence operations, and cooperation with third parties. US Government rights in regard to military secrecy were uphold in

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3692-568: The information stored for archival purposes is rarely accessed, off-line storage is less expensive than tertiary storage. In modern personal computers, most secondary and tertiary storage media are also used for off-line storage. Optical discs and flash memory devices are the most popular, and to a much lesser extent removable hard disk drives; older examples include floppy disks and Zip disks. In enterprise uses, magnetic tape cartridges are predominant; older examples include open-reel magnetic tape and punched cards. Storage technologies at all levels of

3763-573: The initial report may be classified as Top Secret while the sanitized report may be classified as Secret. In other cases, such as the NSA report on the USS Liberty incident (right), the report may be sanitized to remove all sensitive data, so that the report may be released to the general public. As is seen in the USS Liberty report, paper documents are usually sanitized by covering the classified and sensitive portions before photocopying

3834-492: The level of protection needed (hence the term " classified information "). An individual needs a security clearance for access and other protection methods, such as keeping documents in a safe , are stipulated. Few people dispute the desirability of keeping Critical Nuclear Weapon Design Information secret, but many believe government secrecy to be excessive and too often employed for political purposes. Many countries have laws that attempt to limit government secrecy, such as

3905-480: The lower a storage is in the hierarchy, the lesser its bandwidth and the greater its access latency is from the CPU. This traditional division of storage to primary, secondary, tertiary, and off-line storage is also guided by cost per bit. In contemporary usage, memory is usually fast but temporary semiconductor read-write memory , typically DRAM (dynamic RAM) or other such devices. Storage consists of storage devices and their media not directly accessible by

3976-951: The message, such as through government security classification ) and obfuscation , where secrets are hidden in plain sight behind complex idiosyncratic language ( jargon ) or steganography . Another classification proposed by Claude Shannon in 1948 reads that there are three systems of secrecy within communication: Animals conceal the location of their den or nest from predators . Squirrels bury nuts, hiding them, and they try to remember their locations later. Humans attempt to consciously conceal aspects of themselves from others due to shame , or from fear of violence, rejection, harassment, loss of acceptance , or loss of employment . Humans may also attempt to conceal aspects of their own self which they are not capable of incorporating psychologically into their conscious being. Families sometimes maintain " family secrets ", obliging family members never to discuss disagreeable issues concerning

4047-641: The most commonly used data storage media are semiconductor, magnetic, and optical, while paper still sees some limited usage. Some other fundamental storage technologies, such as all-flash arrays (AFAs) are proposed for development. Semiconductor memory uses semiconductor -based integrated circuit (IC) chips to store information. Data are typically stored in metal–oxide–semiconductor (MOS) memory cells . A semiconductor memory chip may contain millions of memory cells, consisting of tiny MOS field-effect transistors (MOSFETs) and/or MOS capacitors . Both volatile and non-volatile forms of semiconductor memory exist,

4118-518: The piece of information , or simply data . For example, the complete works of Shakespeare , about 1250 pages in print, can be stored in about five megabytes (40 million bits) with one byte per character. Data are encoded by assigning a bit pattern to each character , digit , or multimedia object. Many standards exist for encoding (e.g. character encodings like ASCII , image encodings like JPEG , and video encodings like MPEG-4 ). By adding bits to each encoded unit, redundancy allows

4189-427: The pleasure of surprise. This includes keeping secret about a surprise party , not telling spoilers of a story, and avoiding exposure of a magic trick. Keeping one’s strategy secret   – is important in many aspects of game theory . In anthropology secret sharing is one way for people to establish traditional relations with other people. A commonly used narrative that describes this kind of behavior

4260-403: The problem of data remanence . In the context of government documents, redaction (also called sanitization) generally refers more specifically to the process of removing sensitive or classified information from a document prior to its publication, during declassification . Redacting confidential material from a paper document before its public release involves overwriting portions of text with

4331-410: The redaction tool to permanently remove the proposed items. Secrecy Secrecy is the practice of hiding information from certain individuals or groups who do not have the "need to know", perhaps while sharing it with other individuals. That which is kept hidden is known as the secret. Secrecy is often controversial, depending on the content or nature of the secret, the group or people keeping

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4402-423: The same reason, with highly sensitive areas covered with a slip of white paper. In some cases, sanitizing a classified document removes enough information to reduce the classification from a higher level to a lower one. For example, raw intelligence reports may contain highly classified information such as the identities of spies , that is removed before the reports are distributed outside the intelligence agency:

4473-524: The secret, and the motivation for secrecy. Secrecy by government entities is often decried as excessive or in promotion of poor operation ; excessive revelation of information on individuals can conflict with virtues of privacy and confidentiality . It is often contrasted with social transparency . Secrecy can exist in a number of different ways: encoding or encryption (where mathematical and technical strategies are used to hide messages), true secrecy (where restrictions are put upon those who take part of

4544-411: The sensitive information. These products do not always show the user all of the information stored in a file, so it is possible that a file may still contain sensitive information. In other cases, inexperienced users use ineffective methods which fail to sanitize the document. Metadata removal tools are designed to effectively sanitize documents by removing potentially sensitive information. In May 2005

4615-413: The storage hierarchy can be differentiated by evaluating certain core characteristics as well as measuring characteristics specific to a particular implementation. These core characteristics are volatility, mutability, accessibility, and addressability. For any particular implementation of any storage technology, the characteristics worth measuring are capacity and performance. Non-volatile memory retains

4686-422: The stored information even if not constantly supplied with electric power. It is suitable for long-term storage of information. Volatile memory requires constant power to maintain the stored information. The fastest memory technologies are volatile ones, although that is not a universal rule. Since the primary storage is required to be very fast, it predominantly uses volatile memory. Dynamic random-access memory

4757-422: The text, such as the difference between short and tall letters. The exact length of the removed text also remains recognizable, which may help in guessing plausible wordings for shorter redacted sections. Where computer-generated proportional fonts were used, even more information can leak out of the redacted section in the form of the exact position of nearby visible characters. The UK National Archives published

4828-522: The text. Where text is redacted, in Portable Document (PDF) or word processor formats, by overlaying graphical elements (usually black rectangles) over text, the original text remains in the file and can be uncovered by simply deleting the overlaying graphics. Effective redaction of electronic documents requires the removal of all relevant text and image data from the document file. This process, internally complex, can be carried out very easily by

4899-421: The trade-off between storage cost saving and costs of related computations and possible delays in data availability is done before deciding whether to keep certain data compressed or not. For security reasons , certain types of data (e.g. credit card information) may be kept encrypted in storage to prevent the possibility of unauthorized information reconstruction from chunks of storage snapshots. Generally,

4970-417: The visible appearance and is subject to searching and even simple copy and paste extraction. Proper redaction tools and procedures must be used to permanently remove the sensitive information. This is often accomplished in a multi-user workflow where one group of people mark sections of the document as proposals to be redacted, another group verifies the redaction proposals are correct, and a final group operates

5041-441: Was historically called, respectively, secondary storage and tertiary storage . The primary storage, including ROM , EEPROM , NOR flash , and RAM , are usually byte-addressable . Secondary storage (also known as external memory or auxiliary storage ) differs from primary storage in that it is not directly accessible by the CPU. The computer usually uses its input/output channels to access secondary storage and transfer

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