Data Management: Data Preservation and Destruction
Client/Server Audit: One Bite At A Time
Configuring Cisco Denial of Service Security Features - Part 1
Configuring Cisco Denial of Service Security Features - Part 2
Configuring Cisco Lock-and-Key
Configuring Cisco Reflexive Access Lists
Dysfunctional Controls: Useless, Impractical, Inefficient and Poorly-Designed
When Getting the Audit Done Is the Only Thing
Commentary: Quis Custodiet Ipsos Custodes?
Data Management: Data Destruction and Preservation
Planning to auction off your old computer on eBay? Or more likely, give it away to charity? Or send your damaged computer out for repairs? You might want to take a closer look at your disk drive first! Have you ever bought a used computer, possibly at a failed dotcom auction (try http://www.murphyauctions.net/bestof.html) or Government Surplus (try http://www.gsa.gov/Portal/browse/channel.jsp?channelId=-13914&channelPage=/channel/default.jsp)? Ever taken a look at what’s on the hard drive? Perhaps, you are Curious George and like to poke around on the hard drive looking for interesting leftovers. There are many stories about people retrieving confidential information from second-hand computers. Racy love letters, current curriculum vitae, and pornographic pictures are just some of the things you can find. Did the former possessor of the hard drive maintain a list of bank account numbers on the computer? Did the previous owner have a list of PINs for debit or credit cards or passwords for other systems? Is their identity worth stealing? Given how many dotcoms went out of business, you wouldn’t have to look long to find hard drives out there with interesting data.
According to two Massachusetts Institute of Technology (MIT) graduate students (Simson L. Garfinkel and Abhi Shelat), companies and individuals are frequently selling or giving away old computer disk drives with sensitive information still on them. They analyzed 158 disk drives purchased through eBay Inc.’s online auction site, at computer stores, salvage companies and swap meets. The two found they could recover and read data from almost three-quarters of the systems. Previous owners had properly sanitized less than 10 percent. The students recovered personal and corporate financial records (including credit card numbers, bank account numbers, dates of transactions and account balances), medical records, love letters, personal e-mail and pornography. (You can find a summary of their report at http://www.computer.org/security/v1n1/garfinkel.htm.)
There are other examples of this kind of behaviour recorded in the popular press. In 2003, a U.S. state auditor found that at least one computer used by AIDS-HIV counselors was ready for sale to the public even though it still contained files on thousands of people.
Embarrassing (and frightening) to the individuals involved, it still is not life-threatening. Over ten years ago, the GAO reported that the Department of Justice disposed of computer assets and the buyer ultimately retrieved information from the hard drives. Apparently, the buyer recovered information dealing with the witness relocation program for the Northeast! But, the Government doesn’t learn. The GAO again reported in early 2001, that the Department of Energy disposed of computers that the department had not adequately cleaned, exposing data. It might well turn out foreign governments interested in doing espionage are buying disk drives!
There’s another way to look at this. Suppose you buy a formatted drive. You start your system, the drive comes up, and you don’t see any files. You run the DOS format command and don’t see any bad blocks. You use that drive for years and never suspect that it had child pornography on it because that data isn’t part of the blocks that you were looking at. But should someone come in and use forensic tools, they would find it since the data is still there.
So, let’s say you want to sell your old computer, but you don’t want snoopers reading all your old e-mail or getting your bank account number. What do you do? Reformat the drive? Before you look at the answers to these questions, let’s talk a little about how information is actually stored on the disk. A hard disk is magnetic media. In other words, your system stores information on the disk by changing the magnetic characteristics of a certain spot on the disk. As the system writes files to the disk, the system also writes the location of the file to another section of the disk: the index or catalogue. When you delete a file, the system only erases information about the location of the file. The information in the file itself remains on the disk. The same is true should you reformat a disk. In this case, the system erases all information about the location of the files but the information on the disk remains.
Casual computer users often assume that, when used, reformatting permanently deletes the data stored in a file from the computer’s disk drive. It doesn’t. Instead, most operating systems simply change the data to indicate that the file has been deleted, then mark the areas of the hard disk that contain the “deleted” data as being available for reuse by other programs. The commonly-used Microsoft format commands, such as FDISK, for example, verify the integrity of the disk drive blocks, but do not erase files. Moreover, Windows works in the background to actively preserve your deleted files. The Windows Recycle Bin only pretends to delete files, but the Recycle Bin subsystem surreptitiously copies the whole file to a special directory from where you can easily recover it. Should you empty the Recycle Bin, you still can retrieve the file, because the normal OS-level deletion operation kicks in and simply marks the file area as “ready for reuse.” Assuming another program doesn’t overwrite that data, it remains there undisturbed and you can retrieve and read it using a variety of techniques ranging from simple operating system commands to free and commercial forensic software tools. As well, Windows ME and XP have a System Restore function that saves and can restore certain kinds of files, even when you’ve erased them.
Regardless, in less than a minute with your favourite search engine (mine is currently Vivísimo Document Clustering at http://vivisimo.com/), you can find companies that sell utilities specifically made for recovering data from drives that have been reformatted, hit by viruses, or whatever. There are a number of tools that can read information on disks even when someone has formatted the disk. Table 1 provides a short list of some of these products.
Table 1. Data
Recovery Tools
|
Product |
Vendor |
|
Active@ Partition Recovery |
Partition Recovery: http://www.partition-recovery.com/partition.htm |
|
Active@ Uneraser |
Active@uneraser.com: http://www.uneraser.com/undelete.htm |
|
Data Recovery |
Data Guys: http://www.cddataguys.com/ |
|
Data Recovery |
DTI Data Recovery: http://www.dtidata.com/our_products.asp |
|
EasyRecovery DataRecovery |
OnTrack: http://www.ontrack.com/easyrecoverydatarecovery/index.asp |
|
Fast File |
ESS Data Recovery: http://www.dataer.com/fastfile.htm |
|
File Scavenger |
QueTek Consulting Services: http://www.quetek.com/prod02.htm |
|
FinalData Data Recovery Software |
Final Data: http://www1.finaldata.com/ |
|
GetDataBack |
Runtime Software: http://www.runtime.org/ |
|
Media Tools |
ACR Data Recovery Software: http://www.data-recovery-software.com/mtl.htm |
|
R-Studio |
R-TT.com: http://www.r-tt.com/?GGLPR005 |
|
Restorer2000 |
Bitmart.net: http://www.bitmart.net/index.shtml |
|
Stellar
|
Stellar Information Systems: http://www.stellarinfo.com/ |
|
ZAR |
Zero Assumption Recovery: http://www.z-a-recovery.com/ |
Maybe you already know about such utilities, and you’ve gone to the trouble of filling your entire hard drive with zeros. That’ll take care of the commercial recovery utilities, but someone with a few thousand dollars and the know-how could nonetheless recover all your data even from that action. (Read http://www.cs.auckland.ac.nz/~pgut001/pubs/secure_del.html and http://sxm4.uni-muenster.de/stm-en/ for more information on recovering “deleted” data. Should you really want to recover data without building a scanning-tunnelling microscope yourself, check out http://www.datarecoverycompanies.com/. They claim 80 to 90 % of lost data is recoverable and provide a list of companies to help.)
Nevertheless, the only way to make information unavailable on the disk is to overwrite the specific parts of the disk that contain the information. While you could do this manually, it is much more efficient to do this with a disk wiping tool. Tools like this overwrite the entire disk or just the location of a specific file multiple times to make sure that the information is unreadable. The software takes about 30 to 40 minutes per gigabyte to sanitize or scrub the data. Table 2 provides a short list of vendors selling erasure or disk scrubbing software.
Table 2. Disk
Scrubbing Tools
|
Product |
Vendor |
|
Autoclave1 |
Josh Larios: http://staff.washington.edu/jdlarios/autoclave/ |
|
CyberScrub; cyberCide |
Cyberscrub: http://www.cyberscrub.com |
|
Data Scrubber |
Data Devices International : http://www.datadev.com/ds100.html |
|
DataGone |
PowerQuest : http://www.powerquest.com |
|
Eraser |
Heidi Computer Ltd: http://www.heidi.ie/eraser/ |
|
Evidence Eliminator |
Evidence-eliminater.com: http://www.evidence-eliminator.com/product.d2w |
|
Norton Clean Sweep |
Symantec: http://www.symantec.com |
|
QuickClean |
McAfee: http://www.mcaffe.com |
|
Stellar Wipe |
Stellar Information Systems: http://www.stellarinfo.com/ |
|
UniShred Pro |
Los Alamos Technologies: http://www.lat.com/ |
|
Window Washer |
Webroot Software: http://www.webroot.com/wb/products/windowwasher/index.php |
|
Wipe |
SourceForge: http://wipe.sourceforge.net/ |
|
Wiperaser |
Liveye: http://www.liveye.com/wiperaser/ |
1 This software is released under the GNU Public License; hence it is free.
One thing to keep in mind when evaluating these tools is to ensure it meets the Department of Defense Standard (DoD 5220.22). This standard requires that your utility overwrite the disk in several ways: first with zeros, then with ones, then with random numbers between 2 and 9. This makes it much more difficult for anyone to get at the information. These tools do exist, so obviously finding good tools is not the tough part.
Before you go any further, you have to do the tough part. You have to answer the big question: “How valuable is the data on my hard drive?” It does not matter whether you are looking at data destruction or preservation: this is a key question. All paranoia aside, it’s unlikely that anybody cares enough about the data on a home computer to take the time to recover a zeroed-out drive. On the other hand, should the computer come from a business, hospital, or research lab, it’s another story. The right buyer may pay big money for data on those computers.
Even the U.S. Department of Defense uses risk assessment to decide how to dispose of systems. In the summer of 2001, Deputy Secretary of Defense Paul Wolfowitz rescinded a January 2001 Department of Defense policy calling for destruction of all unclassified computer hard drives leaving departmental custody. Wolfowitz’s new disposal guidance will make more computers available for schools and other worthy organizations. Under this new guidance, the minimum requirement for equipment leaving DoD’s custody or control is for someone to overwrite the computer hard drives, but not completely destroy them. DoD still authorizes degaussing and destruction alternatives when there is a particular concern about data sensitivity on the machine. The long-standing practice of destroying hard drives on computers with classified information remains in place. Should you have an interest, you can find the policy direction, entitled “Disposition of Unclassified DoD Computer Hard Drives,” at http://www.c3i.osd.mil/hottopics.html.
You might also want to check out the Department of Defense’s “National Industrial Security Program Operating Manual” at http://nsi.org/Library/Govt/Nispom.html#link5. In the document, the DoD recommends the following steps to dispose of hard drives that contain “moderately” sensitive information:
-
Overwrite all addressable locations with a single character.
-
Degauss with a Type I degausser.
-
Degauss with a Type II degausser.
-
Overwrite all addressable locations with a character, its complement, then a random character and verify.
-
Destroy by disintegration, incineration, pulverization, shredding, or melting.
Amazingly, these steps are not designed for the very highest levels of security. I can only imagine what they do to sanitize really sensitive data! Perhaps, they drop the drives in a vat of lukewarm Coca-Cola™!
But let’s say you want to preserve the data not destroy it. Data destruction is just one side of the coin. The other side is digital preservation, that is, the managed activities to ensure continued access to electronic resources. Access is the key factor here: when you cannot use a resource anymore, it is totally pointless to preserve it. Preservation of data is a key consideration for many organizations. Operational, legal, regulatory and historical needs are just some of the reasons for preserving data. What do you do when you want to preserve the data on the media for an extended period? How long will the data last on the hard drive you just sold or gave away? How long will the tapes you sent to off-site storage continue to hold a charge? Well, either way it is important that you know something about the lifetime of various media and other factors affecting data preservation and destruction.
Media Types and Properties
Below is a brief description of widely used storage media.
Microfilm
Microfilm seems, to many, outdated and behind the times. In our new information economy, electronic imaging is, surely, the way to go when you want to preserve information for posterity. Vital records, insurance claims and applications, loan applications and library records, among others, are some of the documents currently imaged.
Nonetheless, microfilm possesses two simple advantages over most other media used for recording information: it is long-lived and readable by humans with little difficulty. These are pretty basic and crucial advantages. You only can retrieve electronic data when you have the appropriate hardware and software to do the retrieval, and only the foolhardy would argue that we will have all of today’s hardware and software around tomorrow. Even when appropriate equipment is available in ten or twenty years, the electronic medium chosen to carry some specific information could well, by then, have deteriorated to the point of being unusable. Unfortunately, we have many examples of this kind to reflect upon. On the other hand, you can, in a pinch, retrieve information on microfilm with an instrument that has been around for centuries and will continue to exist for as long as humanity exists: the magnifying glass.
Without sounding like a Luddite, microfilm is, in my opinion, an eminently suitable medium for the preservation of information. It is durable (depending upon the type of film you choose), long-lived, and relatively inexpensive. But most of all, the information on it is retrievable by the human eye. Only printing on paper or chiselling in stone can match this!
Microfilm is available in a number of types. Silver halide film on a polyester base, processed and stored in accordance with the existing standards, has proven to last more than 1,000 years. That exceeds my need to preserve that “nastygram” from my Bank!
Magnetic tape
Magnetic tape is a logical media selection. A magnetically coated strip of plastic, where you can encode data; magnetic tape provides relatively inexpensive and large storage capacities. Because tapes are sequentially-accessed and not randomly, access time is slower on tape than on devices like disks or CDs. Tapes are available in a range of sizes and formats. While tape media are still very good for transporting and backing up data, they are not suitable for long term storage because of the limited lifetime of the media. See Table 3 for an approximate lifetime.
Digital Linear Tape
A recent development in tape storage technology is DLT (Digital Linear Tape). DLT is a cartridge tape and offers significant improvements in data access rates over magnetic tape. Moreover, DLT is durable (medium lifetime 30 years) and has very large capacity (10 to 80 gigabytes of compressed data per volume), with a low cost. There are other variants of high capacity tapes but you may want to question the longevity of such technologies.
CD-ROM (Compact Disk–Read Only Memory)
Optical disk technology is capable of storing large amounts of data that you can read but not alter. CD-ROMs all conform to size and format standards and are well suited for storing software applications, graphics, sound and video.
CD-R (Compact Disk-Recordable)
Based on WORM technology, a CD-R system can store large amounts of data, even though a single CD-R can hold only 0.64 gigabytes. CD-R drives have been improved to enable multi-session recording (that is, you can add additional data over time). The “write-once recordable” CD (CD-R) is inexpensive and CD juke boxes have been available for quite sometime.
DVD-R (Digital Versatile Disk-Recordable)
The “write-once recordable” digital versatile disk (DVD-R), considered a replacement for CDs, are on the market. Current single-sided DVD-R holds 4.7 gigabytes of data. The storage capacity will double when double-sided disks become available in the near future. DVD-R drives in juke box configuration with a capacity of 4 terabytes are on the market. Often, these juke boxes are backward compatible so the devices can handle a mixture of CDs and DVDs.
WORM
WORM drives read data in a fashion similar to CD-ROM drives, but they also can write data to disk (though this writing is permanent; hence the term, ‘Write-Once-Read-Many’). With WORM, a laser burns holes directly onto the surface of the disk. Since these holes reflect much less light than intact disk areas, the device uses the resultant decrease in beam intensity to denote the data stored on the disk. A WORM drive uses removable media divided into consecutively numbered, fixed-size sectors that the device can access in any order, similar to a hard disk.
Organizations have used WORM optical disks and supporting juke boxes for data archival. WORM optical disks and the juke boxes capacity can go up to 12 gigabytes per medium. Most WORM drives can store 800 megabytes of data per cartridge, while CD-ROM drives have 640 megabytes of storage space. But as CD and DVD become more popular, this technology is now becoming obsolete. >Factors suggesting its demise are that the media and system are more expensive than other media.
Magnetic hard disk
A hard disk, as opposed to a floppy disk, is a magnetic disk that can store large quantities of data. Hard disks or drives come in various sizes and it is not unusual to buy a low end computer with a 40 gigabyte drive. However, hard disk storage is more expensive than other storage media.
Magneto-Optical
Magneto-optical (MO) disks are also a popular choice among the high density media with reasonable storage capacity (5.2 gigabytes on a single MO disk). MO disks are 5 ¼-inches. Data is written on an MO disk by both a laser and a magnet.
MO gives you high-capacity disks perfect for quick file retrieval (access times are in the sub-25ms range) at a low cost per gigabyte.
Media Lifetimes
In addition to capacity, access, legal requirements, maintenance, reliability, cost of media and the system as a whole, I/O speed, and durability of the media, you should consider the expected lifetimes of any selected medium. There is reasonably widespread (though by no means universal) awareness of the fact that digital storage media have severely limited physical lifetimes. The National Media Lab (http://www.nml.org) has published test results for a wide range of tapes, magnetic disks, CD-ROMs, and other media, showing that a tape, disk, or even CD picked at random (that is, without prior evaluation of the vendor or the specific batch of media) is unlikely to have a lifetime of even five years. Notwithstanding their opinion, Table 3 as an example provides expected and typical lifetimes for various media.
Table 3. Expected Lifetimes of Selected Media in Years|
Medium |
Ideal Lifetime |
Normal Lifetime |
Note |
|
CD-R |
5-100 |
2-30 |
Dye representing data less stable over time compared to pits used with commercially recorded CD-ROMs. |
|
CD-ROM |
30-200 |
5-50 |
Uses actual pits and lands on a metallic surface to encode data; fragile surface |
|
DLT |
30-100 |
5-20 |
Should be rewound periodically to release tension |
|
DVD |
100 |
20 |
Higher-density media more susceptible to environmental changes |
|
DVD-R |
20-30 |
10 |
Like CD-R, less stable than commercially recorded media |
|
Hard drive |
<100 |
10-20 |
Lifetime a function of the integrity of the electro-mechanical assembly |
|
Hard disk cartridge |
<100 |
20-40 |
Lifetime a function of the integrity of the media |
|
Magnetic tape |
30-100 |
5-20 |
Should be rewound periodically to release tension |
|
Microfilm |
500 |
100-200 |
Standard for archival purposes; depends on type of film used |
|
Magneto-Optical |
5-100 |
2-30 |
Multiple format standards |
|
WORM |
30-200 |
5-50 |
Format less standardized than CD-ROM or DVD |
Table adapted from Dark Ages II
(Prentice Hall, 2002) by Bryan Bergeron.Vendors and media scientists may argue vehemently about such numbers, but accurate estimates are ultimately largely irrelevant, since the physical lifetime of media is rarely the constraining factor for digital preservation. Should any company introduce archival quality media in the market; they would probably fail, since they would quickly be made obsolete—despite their physical longevity—by newer media having increased capacity, higher speed, greater convenience, and lower price. This is a natural outgrowth of the exponential improvement in storage density, speed, and cost characterizing digital media development for the past several decades. The market makes older storage media obsolete as newer, better media become available. (Do any of you remember when all you wanted was a 20 megabyte hard drive?) The short lifetimes of eight-inch floppy disks, tape cartridges and reels, hard-sectored disks, and seven-track tapes, among others, demonstrate how quickly storage formats become inaccessible.
In addition, you should read carefully the “fine print” when it comes to statements about media lifetime estimates. DAT DDS tapes, for example, have a 10 year estimated lifetime. What that actually means is that should you use a tape once to record data and put it on a shelf in a temperature and humidity controlled environment, likely you can read it in 10 years. Divide that by some factor when you store it under less than ideal conditions. Divide it again by some factor when you read and write to the media or otherwise handle it.
So, it appears the media itself is vulnerable to decay and obsolescence. The standard lifetime of a particular disk or tape appears to be less than a decade; and you must copy or refresh the data stored on these media at regular intervals. A recent Canadian National Research Council study discussed the effects and implications of long-term commitments in scientific data management, with respect to both selection of data for long-term retention and media obsolescence. Further (and paradoxically), they concluded that data collected before the advent of computers and stored on “archival media” (paper) must be put into electronic form for wide and effective use today. They also concluded that such data can add enormous value to research efforts, particularly for studies examining long-term trends, but are costly to migrate.
The top priority is extending the usability of magnetic and optical media by stabilizing their structure and limiting the ability of internal and external factors to cause deterioration. It is important to identify life expectancy for existing media and to select the best media for storing new files in this digital world.
Preservation Concerns
But media lifetime is only part of your problem. Preserving a printed book for decades or even centuries has been relatively easy. First, paper is usually a very durable material. Second, humans can extract information from a book by a simple process: reading. Third, understanding the information is possible since the written languages have not changed totally and there are human experts who can translate the documents into modern language. A friend of mine’s sister specializes in Old English and I can read Moliére’s Tartuffe written in early 17th century French.
But, electronic resources differ in a fundamental way from printed resources. An application has to interpret every electronic resource before it can be displayed to and understood by humans. You can interpret any string of bits in countless ways, depending on the resource type and the application used. And this application, for instance, Microsoft Word 2002 for Windows, requires an operational environment, that is, hardware, operating system running on the hardware, and drivers and other support software.
If the information technology you use were stable, then preserving data would be a simple task. But our technological infrastructure is changing with ever increasing speed. Technical obsolescence threatens your data in many different ways.
As pointed out, the media electronic resources you store data on may become unreadable either because the media—diskette, tape or CD ROM disk—is physically destroyed, or because you cannot read the media anymore although it still is physically in good condition.
File formats and compression schemes are also constantly changing. Sometimes there is a real reason for this, for instance compression techniques have improved quickly, improving efficiencies of some data transmissions. But one might cynically suggest that it is all too common for vendors to make changes to force customers to buy new versions of their products. Reluctance to use standards—or to use them properly—may also benefit a company from a marketing and sales point of view.
Advances in computer design have been spectacular, and it seems certain that the current development rate, as specified by Moore’s Law, will not abate during the next 10 to 15 years. Should this Law continue to apply for the next 30 years; our children will have computers that are a million times faster than their current system. It is almost certain that these machines will do at least the same things that the current systems do, but what else can they do? If the future computers are speech or vision controlled, could or would the future users get accustomed to user interfaces common in 2003?
Some experts have suggested that standards will solve our problems. But you may never see the standardization of some relevant technical features, and technical development also will change the standards we rely on. For example, there are already two, very different versions of the JPEG image compression standard even though the first JPEG version is less than 10 years old. How many JPEG versions will we have 100 years from now? You are probably aware of SGML, HTML, and XML. Maybe even SAML. But, are you also familiar with cHTML, HDML, WML, S-HTML, XHTML, VML, SMIL, MathML, ORM-ML, XrML, MNML, QAML, and DAML among others? Which of these standards, if any, will survive?
Successful long-term storage and preservation of documents and data involves looking at the aforementioned issues. Let’s look in turn and in more detail at the following:
-
Intentional or unintentional destruction
Loss through misplacement
Storage medium/media degradation
Media and hardware obsolescence
Format and software obsolescence
Intentional or Unintentional Destruction
Active files on computers, especially shared data on network servers, are constantly changing. In the normal course of business, you open, close, edit, alter, modify, rename or delete files. They are subject to manipulation in ways that static paper documents, stored in file cabinets, are not. Word-processed documents or e-mail messages may take on a more-or-less permanent form once completed, but financial records, customer databases, and other data compilations by their very nature are dynamic. Even the act of opening files may fundamentally change an important characteristic, such as automatically-generated dates or calculations of interest.
Many computer network administrators will routinely create back-ups of network data. Many administrators keep these backups forever, but others will do exactly what they are supposed to do, and overwrite them in the normal course of business with more current data.
Distinct from the routine churning of data resulting in the inadvertent destruction of data is the potential intentional destruction. Individuals faced with potential lawsuits or employment dismissal might immediately delete damaging e-mail and word-processing files. Even when the destruction of electronic evidence, inadvertent or wilful, is ultimately unsuccessful, the cost of locating and recovering the data will increase substantially. So while the complete physical destruction of electronic data is difficult or impossible, it is relatively easy to render the data inaccessible or retrieval too costly.
Organizations must implement security measures to protect records against either deliberate or accidental alteration. Some possibilities include:
-
maintaining controlled access to data whether it is on-line or off-line in a secure storage facility with only authorized staff with rights to access the records;
compliance and audit programs to ensure security procedures are maintained; and,
providing ‘read-only’ access to the records.
This paper does not deal directly with data security but with data management, with security being an integral component. You can obviously pick up any good security resource and learn how to prevent or recover from accidental or intentional access, misuse or destruction of data.
Loss through Misplacement
Loss through misplacement is pretty straightforward. Even where you have good media and good procedures, they don’t mean a thing when you cannot find the media. So, your company should institute a schedule of on-site and off-site media audits. Find out the media is missing when you can still do something about it. Not when it is too late!
Storage Medium/Media Degradation
Magnetic and optical media and the information stored on them degrade over time, which destroys the stored data. There are events or agents that can accelerate the degradation process. Table 4 shows some factors that accelerate the rate of degradation.
Table 4. Degradation Accelerants|
Factor |
At Risk |
Effects/Examples |
|
Biological infestation |
CD-R, tapes |
Insects, rodents, moulds, and bacteria destroy some plastics. |
|
Bright light |
CD-R, DVD-R, microfilm |
Sunlight or artificial light causes accelerated photochemical deterioration in plastics. |
|
Contamination |
CD-ROM, CD-R, DVD, DVD-R, tapes |
Gases from untreated wood cloud plastic surfaces; and impurities promote oxidation of metal films. |
|
Magnetic field |
All digital media |
Demagnetize media. |
|
Humidity (high) |
CD-ROM, CD-R, DVD, DVD-R, magnetic disks |
Plastics swell and cloud; film blemishes; and metals oxidize. |
|
Humidity (low) |
EEPROM, RAM, flash memory disk |
Static charges develop and can discharge through media. |
|
Mishandling |
All media |
Glass shatters; plastic snaps; microfilm scratches and tears; and surface pollution. |
|
Temperature (cold) |
Glass WORM disks, tape and hard drive cartridges |
Glass fractures; plastic becomes brittle; and metals contract. |
|
Temperature (hot) |
All digital media |
Metals expand and deform; tapes delaminate; plastics deform and melt. |
|
Pollution (particulate and gases) |
All digital media |
Plastic oxidizes; plastics cloud; and metal contacts corrode. |
|
Temperature swings (rapid/wide) |
All digital media |
Metal films, plastic and glass crack, buckle and tear or break; electrical contacts within ICs and between ICs and their sockets separate; and read and write heads in hard disks become misaligned. |
Table adapted from Dark Ages II
(Prentice Hall, 2002) by Bryan Bergeron.So, you need to handle and store media properly to get the maximum lifetime. Any factor shown above could reduce the life or effectiveness of your chosen media.
Media and Hardware Obsolescence
Ah, perhaps in the good old days you had a TRS-80 or an Apple Lisa. Those were the days! But as you have figured out: computer technology is subject to on-going technological obsolescence. Hardware and software quickly become outdated as new upgrades and versions come onto the market. Electronic material created under older systems becomes unreadable (and hence inaccessible) in the original form after relatively short periods of time. To illustrate, Table 5 lists some of the hardware that has become obsolete in the short history of the microcomputer.
Table 5. Obsolete Microcomputer Hardware Platforms|
Platform |
|
Apple I, II, IIe, IIc, IIsi, III, Lisa, Macintosh |
|
Commodore 64 |
|
IBM PC-AT, PC-JR, PC-XT |
|
Osborne |
|
PET |
|
Portable PC |
|
Radio Shack TRS-80 |
|
Sinclair |
Don’t forget about IBM’s Series 1, S/34, S/36, S/38 and AS/400! We could get quite an impressive list of obsolete hardware when we include Amdahl, Burroughs, NCR, Sperry-Rand, and Univac to name a few.
So whole systems become obsolete, but so does the media they use. Media obsolescence manifests itself in several ways:
-
the medium itself disappears from the market;
-
appropriate drives capable of reading the medium are no longer produced; and,
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media-accessing programs or device drivers capable of controlling the drives and deciphering the encodings used on the medium are no longer written for new computers.
Often, the act of upgrading to a new computer system means abandoning an old storage medium. The dual problems of short media lifetime and rapid obsolescence have led to the nearly universal recognition that you must refresh or copy digital information to new media every few years. You might think that copying is a relatively straightforward solution to these media problems. Though it is not trivial; in particular, the copy process must avoid corrupting documents via compression, encryption, or changing data formats.
In addition, as media become denser, each copy cycle aggregates many disks, tapes, or other storage units onto a single new unit of storage; for example, a compact disk or digital versatile disk. This raises the question of how to retain any labelling information and metadata associated with the original media since you cannot practically write the contents of the labels of 400 floppy disks to fit on the label of a single CD. So, you must digitize the label information to ensure that it continues to accompany the data it describes. But whereas labels are d