Adware: software that repeatedly displays a particular message or Web site. Individual examples may seem harmless, but as infections multiply the machine may bog down.
Backdoor: similar to a Trojan, a backdoor ensures entry for an intruder.
Botnets: collections of computers that have been infected by a bot master and are under his control.
DoS (Denial of Service) Attack: saturating a Web site with file requests (typically launched by the zombies of a botnet) so that the site ceases to function.
Drive-by download: software that is installed without the user’s knowledge when visiting a malicious Web site.
Keyloggers: often loaded by Trojans, keyloggers record log-on activity and transmit it to criminals.
Malware: any unwanted software, such as worms, viruses, and Trojans.
Pharming: any of several methods used to divert Web traffic from a legitimate Web site to a bogus site, usually to harvest logons.
Phishing: spam that tries to trick the recipient into giving personal information that could be used for identity theft, typically on the pretext that the recipient’s online bank or eBay account suddenly requires “verification.”
Polymorphic technology: malware that is embodied in multiple files with random names to complicate detection, and (typically) if one file is deleted the surviving files will replicate and replace it.
Rootkit: an infection that prevents certain files from being detected by the operating system.
Spam: Unwanted e-mail, churned out in the millions, often by zombies.
Spyware: programs that record the user’s activities, such as web sites visited (for advertising purposes) or passwords entered (for criminal purposes.)
Trojans: malware that loads other malware (such as keyloggers or botnet controllers) after being activated by the user, who has been tricked into believing it is something else.
Virus: malware that propagates by attaching itself to legitimate computer files, or to e-mail.
Worms: malware that actively propagates itself through the network. Zombies: individual members of a botnet.