Spam
Spam is electronic junk mail which is sent to numerous recipients in the hope that one might respond. As apposed to UCE, or "unsolicited commercial email," Spam is often illicit in nature, and has come to be a major commercial and legal issue in the world of Internet commerce today.
Most email providers offer some form of spam-blocking with varying degrees of effectiveness.
Antivirus
Antivirus software is a system that prevents the introduction of infectious programs, such as viruses and trojans, into a network or individual computer. These malicious programs are often introduced through email.
Antivirus software works by scanning files to see if they match known "definitions" or descriptions of existing viruses and then isolating and eliminating these elements of infectious code. Some antivirus software also scans the system to see if there is any suspicious behavior, such as alterations in important system files, or the use of uncommon or unusual ports that may be used by the virus to send data.
