Tens of thousands of malware exist, with more being created each day. Although once most common in DOS or Windows, computer malware today can cause a great amount of damage by exploiting vulnerabilities in corporate networks, email systems and Web sites.
Joke program: A malware-like program that often manipulates the appearance of things on a computer monitor
Trojan horse: An executable program that does not replicate but instead resides on systems to perform malicious acts, such as opening ports for hackers to enter. A Trojan program often uses ports to gain access to computers. An application that claims to rid your computer of malware when it actually introduces malware onto your computer is an example of a Trojan program. Traditional anti-malware solutions can detect and remove malware but not Trojans, especially those already running on the system.
Malware: A program that replicates. To do so, the malware needs to attach itself to other program files and execute whenever the host program executes.
ActiveX malicious code: Code that resides on Web pages that execute ActiveX™ controls
Boot sector virus: Malware that infects the boot sector of a partition or a disk
COM and EXE file infector: An executable program with .com or .exe extension
Java malicious code: Operating system-independent malware code written or embedded in Java™
Macro malware: Malware encoded as an application macro and often included in a document
VBScript, JavaScript or HTML malware: Malware that resides on Web pages and downloaded through a browser
Worm: A self-contained program or set of programs able to spread functional copies of itself or its segments to other computer systems, often through email
Test malware: An inert file that acts like real malware and is detectable by anti-malware scanning software. Use test malware, such as the EICAR test script, to verify that your anti-malware installation scans properly.
Packer: A compressed and/or encrypted Windows or Linux™ executable program, often a Trojan horse program. Compressing executables makes packer more difficult for anti-malware products to detect.