Database security

Security is another important database issue. Data residing on a computer is under threat of being stolen, destroyed, or modified maliciously. This is true whenever the computer is accessible to multiple users but is particularly significant when the computer is accessible over a network. The first line of defense is to allow access to a computer only to authorized, trusted users and to authenticate those users by a password or similar mechanism. But clever programmers have learned how to evade such mechanisms, designing, for example, so-called computer viruses--programs that replicate themselves and spread among the computers in a network, "infecting" systems and potentially destroying files. Data can be stolen by devices such as "Trojan horses"--programs that carry out some useful task but contain hidden malicious code--or by simply eavesdropping on network communications. The need to protect sensitive data (e.g., for national security) has led to extensive research in cryptography and the development of encryption standards for providing a high level of confidence that the data is safe from decoding by even the most powerful computer attacks. The term computer theft, however, usually refers not to theft of information from a computer but rather to theft by use of a computer, typically by modifying data. If a bank's records are not adequately secure, for example, someone could set up a false account and transfer money into it from valid accounts for later withdrawal.