Computer systems have become modular over the last few years, and one of the benefits of this is removable media. Disk drives that once cost thousands of dollars now cost hundreds or even less. What once took up a whole room can easily be put in a coat pocket. Removable media refers to any type of storage device (such as a floppy drive, magnetic tape cartridge, or CD-ROM) that can be removed from the system. Several of the more common removable media are covered in this section.
The important thing to remember is that removable media is subject to viruses, physical damage, and theft. If a CD-ROM is stepped on or scratched, it probably will not work properly. If stolen, it will not be available and the information it contained will be gone forever.
The following sections discuss the most common types of removable media in use today, and what physical and operational measures are needed to safeguard your removable media.
One of the oldest forms of removable media is magnetic tape. Magnetic tapes come in a variety of types and sizes. Older tapes were reel-to-reel and were bulky and very sensitive to environmental factors such as heat and moisture. Newer tapes are cartridge or cassette-oriented and are smaller and much more durable. Some of the new tape technologies can store on a single tape what would have required a 10-foot-by-10-foot tape vault. This single tape is slightly larger than a CD-ROM carrying case.
Magnetic tapes have become very fast, and they can hold enormous amounts of data. They are commonly used to back up systems and archive old data. The major concern with tape involves physical security. It is very easy to remove one from the premises undetected.
Tape can be restored to another system, and all of the contents will be available for review and alteration. It is relatively easy to edit a document, put it back on the tape, and then restore the bogus file back to the original computer system. This of course, creates an integrity issue that may be difficult to detect.
Tapes can also become infected with viruses, and they can infect a system during the data recovery process. Files going onto a tape drive should be scanned to ensure that they are virus free.
The CD Recordable (CD-R) is a relatively new technology that allows CDs to be made or burned on a computer system. CD-Rs operate like a regular CD, and they can be burned quickly. Most new computer systems come standard with a CD-R "burner," or CD-R drive. Data can be backed up or restored from the CD-R very quickly. CD-Rs are susceptible to computer viruses, and an infected file on the computer that is transferred to the CD-R will infect another system when the file is downloaded. Data theft is also very easy with a CD-R. An attacker can get on a system that has a CD-R and copy data from hard disks or servers. Files written to a CD-R can contain viruses just like any other files. This means that a CD can be a carrier. All files should be scanned for viruses before they are written to or read from a CD. Some older CD-Rs are susceptible to erasure by sustained exposure to sunlight. It is generally a good idea to keep CD-Rs out of environments that are high in ultraviolet (UV) light. Most software products now come on CD, and they can disappear quite easily. This type of theft can cost a company thousands of dollars.
Hard drives today are very small, and they can store a great deal of data. Usually, hard drives can be quickly removed from systems, and portable hard drives can be easily attached. Software that creates an exact copy, or image, of a drive can be used to download a system onto a hard drive in minutes. Many of the hard drives available today use USB or parallel ports to connect, and some operating systems will install them automatically using Plug and Play technology. An attacker can attach a USB hard drive and then copy files from a workstation. This can happen in a matter of minutes with very little possibility of detection.
Another aspect of hard drive security involves the physical theft or removal of the actual drives. If a drive containing key information is stolen, it may be difficult to replace unless a recent backup has been performed. Hard drives are also susceptible to viruses, as they are the primary storage devices for most computers. Additionally, hard drives are susceptible to vibration damage. Dropping a hard drive will usually result in premature failure of the unit.
Most computer systems provide the capability to accept floppy and other types of diskettes. These diskettes have properties similar to hard drives, although they usually store smaller amounts of data. They are one of the primary carriers of computer viruses, and they can be used to make copies of small files from hard disks.
Diskette drives are very rugged, and they can take all kinds of physical abuse. If the media in the drive becomes scratched, the data will be lost. Diskettes are very sensitive to erasure by magnetic fields.
You have been asked to help troubleshoot a problem that is occurring in your school's computer lab. Students are complaining about viruses that are infecting the floppy disks they bring to school. How can you help remedy this situation?
You will want to ensure that all of the systems in your school lab computers are running antivirus software, and that this software is kept up-to-date. Doing so will prevent known viruses from entering the school's system and being transferred to student files. You may also want to evaluate whether or not the school computers should have removable media installed on their systems. Several manufacturers now sell systems called thin clients that do not provide any disk storage or removable media on their workstations. Thin clients use dedicated servers to download applications, data, and any other information they need to have in order to run. This eliminates the danger of viruses being introduced from student disks.
Flash cards, also referred to as memory sticks, are small memory cards that can be used to store information. A system that has a flash card interface usually treats flash cards as if they were a hard drive. Flash cards can carry viruses, or they can be used to steal small amounts of information from systems that support them.
Flash cards are coming down in price and are becoming standard on many computer systems. Most PDA devices have the ability to accept flash cards, making them susceptible to viruses that are targeted at PDAs. So far, this has not been a big threat, but you can bet it will become one as these devices become more popular.
Smart cards are usually used for access control and security purposes. The card itself usually contains a small amount of memory that can be used to store permissions and access information. Smart cards are difficult to counterfeit, but they are easy to steal. Once a thief has a smart card, they have all the access that the card allows. To prevent this, many organizations do not put any identifying marks on their smart cards, making it harder for someone to utilize them.
Many European countries are beginning to use smart cards instead of magnetic strip credit cards because they offer additional security and can contain larger amounts of information. The use of smart cards is also growing because they offer more security than traditional magnetic strip cards.