Malware, short for malicious software , is an umbrella term used to refer to a variety of forms of hostile or intrusive software , including computer viruses , worms, Trojan horses , ransomware, spyware, adware, scareware, and other intentionally harmful programs. It can take the form of executable code, scripts, active content, and other software . Malware is defined by its malicious intent, acting against the requirements of the computer user — and so does not include software that causes unintentional harm due to some deficiency.
Programs supplied officially by companies can be considered malware if they secretly act against the interests of the computer user. An example is the Sony rootkit, a Trojan horse embedded into CDs sold by Sony , which silently installed and concealed itself on purchasers' computers with the intention of preventing illicit copying; it also reported on users' listening habits, and unintentionally created vulnerabilities that were exploited by unrelated malware.
Antivirus software and firewalls are used to protect against malicious activity, and to recover from attacks.