What is Malware/Virus/Worm ?

What is Malware?

A malware is a program that performs unexpected or unauthorized, but always malicious, actions. It is a general term used to refer to viruses, Trojans, and worms. Malware, depending on their type, may or may not include replicating and non-replicating malicious code.

Due to the many facets of malicious code or a malicious program, referring to it as malware helps to avoid confusion. For example, a virus that also has Trojan-like capabilities may be called malware.

What is a virus?

A computer virus is a program – a piece of executable code – that has the unique ability to replicate. Like biological viruses, computer viruses can spread quickly and are often difficult to eradicate. They can attach themselves to just about any type of executable file and are spread as files that are copied and sent from individual to individual.

In addition to replication, some computer viruses share another commonality: a damage routine that delivers the virus payload. While payloads may only display messages or images, they can also destroy files, reformat your hard drive, or cause other damage. If the virus does not contain a damage routine, it can cause trouble by consuming storage space and memory, and degrading the overall performance of your computer.

What is a Trojan?

A Trojan is a malware that performs a malicious action, but has no replication abilities. Coined from Greek mythology's Trojan horse, a Trojan may arrive as a seemingly harmless file or application, but actually has some hidden malicious intent within its code.

Trojan malware usually have a payload. When a Trojan is executed, you may experience unwanted system problems in operation, and sometimes loss of valuable data.

What is a worm?

A computer worm is a self-contained program (or set of programs) that is able to spread functional copies of itself or its segments to other computer systems. The propagation usually takes place via network connections or email attachments.

More recent worms have also discovered ways to propagate using Instant Messengers, via file sharing applications, and by collaborating with other malware such as Trojans or other worm variants. WORM_BAGLE.BE, for example, forms a vicious worm-Trojan cycle with TROJ_BAGLE.BE, in which the worm mass-mails copies of the Trojan, and the Trojan downloads copies of the worm. Additionally, the FATSO family is a family of worms that propagate via an instant messaging application and a popular peer-to-peer file sharing application.

Some worms may have an additional payload, such as preventing a user from accessing antivirus Web sites, or stealing the licenses of installed games and applications.