Programs officially supplied by companies can be considered malware if they secretly act against the interests of the computer user. For example, Sony sold the Sony rootkit, which had a Trojan horse embedded into CDs, and 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.
Protection against malware involves the prevention of malware software gaining access to the target's computer, and for this purpose antivirus software, firewalls and other strategies can be used to try to protect against the introduction of malware, to check for the presence of malware and malicious activity, and to recover from attacks.
Many early infectious programs, including the first Internet Worm, were written as experiments or pranks. Today, malware is used by both black hat hackers and governments, to steal personal, financial, or business information.
Malware is sometimes used broadly against government or corporate websites to gather guarded information, or to disrupt their operation in general. However, malware can be used against individuals to gain information such as personal identification numbers or details, bank or credit card numbers, and passwords.
Since the rise of widespread broadband Internet access, malicious software has more frequently been designed for profit. Since 2003, the majority of widespread viruses and worms have been designed to take control of users' computers for illicit purposes. Infected "zombie computers" can be 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.