Microsoft® Exchange Server 2007 Administrator's Companion

Computer Viruses

This section expands on computer viruses in general and discusses some implications for viruses on Exchange Server 2007.

What Is a Virus?

A virus is a piece of code that attaches itself to other programs or files. When these files run, the code is invoked and begins replicating itself. The replication occurs over the network. Viruses can now exploit the vulnerabilities of nearly every platform.

Some viruses reside in memory after the original program is shut down. When other programs are executed, the virus attaches itself to these new programs until the computer is shut down or turned off. Some viruses have a "dormant" phase and appear only at certain times or when certain actions are performed.

There are many types of viruses. Some ...