discusses rules for using your computer. You should also read Computer Vulnerabilities in the Vulnerability to Technical Operations module,
which describes in nontechnical language the security and other vulnerabilities of
computer networks that make some of these rules necessary.
Many aspects of computer use are governed by your organization's policy rather than by law or federal government regulation. Many government agencies and defense contractors specify the security procedures and prohibited or questionable activities discussed below.
The following activities, while not absolutely prohibited, are almost always inappropriate. Individuals may be asked to justify their reasons for engaging in such activities.
As a result of the Internet and e-mail, there has been a sharp increase in security incidents involving the accidental disclosure of classified and other sensitive information. One common problem occurs when individuals download a seemingly unclassified file from a classified system, and then fail to carefully review this file before sending it as an attachment to an unclassified e-mail message. Too often, the seemingly unclassified file actually has some classified material or classification markings that are not readily apparent when the file is viewed on line. Sending such material by e-mail is a security violation even if the recipient has an appropriate security clearance, as e-mail can be monitored easily by unauthorized persons. See E-Mail Pitfalls in Computer Vulnerabilities.
More important, even if the downloaded file really is unclassified, certain technical procedures are required prior to sending that file by e-mail or on diskette to anyone else. A file downloaded from a classified network may have recoverable traces of classified information. This happens because data is stored in "blocks." If a document does not take up an entire block, the remainder of that block may have recoverable traces of data from other files. (See Security of Hard Drives for further information on this.) Your system administrator must follow an approved technical procedure for removing these traces before the file is treated as unclassified.
One organization had so many violations dealing with downloading and retransmitting unclassified files from its classified system that it found it necessary to lock its computer drives. This means that only the system administrator can download from the classified system. The system administrator processes the material and authorizes transmittal by e-mail as appropriate.
Secrets in the computer require the same protection as secrets on paper. Information can be recovered from a computer hard drive even after the file has been deleted or erased by the computer user. It is estimated that about a third of the average hard drive contains information that has been "deleted" but is still recoverable. 1
When you delete a file, most computer operating systems delete only the "pointer" which allows the computer to find the file on your hard drive. The file itself is not deleted until it is overwritten by another file. This is comparable to deleting a chapter heading from the table of contents of a book, but not removing the pages on which the chapter is written. Some networks may be configured to "wipe" or purge the hard drive when information is deleted, but most are not.
Computers on which classified information is prepared must be kept in facilities that meet specified physical security requirements for processing classified information. Special procedures may also be appropriate when working with some types of sensitive but unclassified information. At a miniumum, special procedures for clearing hard drives are appropriate prior to disposing of old computers on which sensitive information has been prepared.
Check with your security office concerning rules for traveling with a laptop on which sensitive information has been prepared. Laptop computers are a particular concern owing to their vulnerability to theft.
Passwords are used to authenticate an individuals right to have access to certain information. Your password is for your use only. Lending it to someone else is a security violation and may result in disciplinary action against both parties. Never disclose your password to anyone. Memorize it do not put it in writing. If you leave your terminal unattended for any reason, log off or use a screen lock. Otherwise, someone else could use your computer to access information they are not authorized to have. You will be held responsible if someone else uses your password in connection with a system transaction.
Do change your password regularly. Use a password with at least six and preferably eight characters and consisting of a mix of upper and lower case letters, numbers, and special characters such as punctuation marks This mix of various types of characters makes it more difficult for a hacker to use an automated tool called a "password cracker" to discover your password. Cracking passwords is a common means by which hackers gain unauthorized access to protected systems.
"Social engineering" is hacker-speak for conning legitimate computer users into providing useful information that helps the hacker gain unauthorized access to their computer system.
The hacker using social engineering usually poses as a legitimate person in the organization (maintenance technician, security officer, inexperienced computer user, VIP, etc.) and employs a plausible cover story to trick computer users into giving useful information. This is usually done by telephone, but it may also be done by forged e-mail messages or even in-person visits.
Most people have an incorrect impression of computer break-ins. They think they are purely technical, the result of technical flaws in computer systems which the intruders are able to exploit. The truth is, however, that social engineering often plays a big part in helping an attacker slip through security barriers. Lack of security awareness or gullibility of computer users often provides an easy stepping stone into the protected system if the attacker has no authorized access to the system at all.
Laptop computers are a prime target for theft for the value of the information on them as well as for the value of the computer. According to Safeware, a computer insurance firm in Columbus, Ohio, 309,000 laptop computers were stolen in the United States during 1997. There is also a high risk of theft during foreign travel. See Theft of Laptops and Theft While Traveling.
The best protection for information on your laptop is to encrypt all sensitive files and e-mail. A variety of keys, cards, and other physical means of preventing unauthorized access to information on a laptop are now coming on the market. Evaluate the various alternatives to see if one of them meets your needs.
Here are some other guidelines for protecting laptops:
1. Alex Markels, The messy business of culling company files. The Wall Street Journal, May 22, 1997, p. B1