Malware is software designed to infiltrate or damage a computer system, without the owner’s consent. The term is a portmanteau of “mal-” (or perhaps “malicious”) and “software”, and describes the intent of the creator, rather than any particular features. Malware is commonly taken to include computer viruses, worms, Trojan horses, spyware and adware. Many users call any piece of malware a “computer virus”, regardless of type, sometimes limiting the term to malware other than spyware or adware (worms, viruses proper, and Trojans).

pop-ups galoreMalware should not be confused with defective software, that is, software which has a legitimate purpose but contains errors or bugs.

A slightly more hostile intent can be found in programs designed to vandalize or cause data loss. Worms such as the Code Red worm or Ramen worm fall into the same category. Designed to vandalize Web pages, these worms may seem like an online equivalent of graffiti tagging, with the author’s name or affinity group appearing everywhere the worm goes.

Revenge is sometimes a motive to write malicious software. A programmer or system administrator about to be fired from a job may leave behind backdoors or software “time bombs” that will allow them to damage the former employer’s systems or destroy their own earlier work.

However, since the rise of widespread broadband Internet access, a greater portion of malicious software has been focused strictly on a profit motive. For instance, since 2003, the majority of widespread viruses and worms have been designed to take control of users’ computers for black-market exploitation. Infected “zombie computers” are used to send email spam, to host contraband data such as child pornography, or to engage in distributed denial-of-service attacks as a form of extortion.

The usual advice stands

Scan your machine once a week for anything suspicious. Keep your antivirus up to date, and avoid downloading and installing anything that is suspicious.