Malware is any software that behaves in a fashon that is hostile to the computer user. Malware includes any software that operates without the computer user's consent and includes a whole range of hostile software such as viruses, spyware, adware, worms, trojans, and hacker tools. Malware may do a range of damage to a computer from making the operating system useless to deleting all the data. Malware may do minor damage and only display advertisements or attempt to replicate itself to other computer systems. Malware may try to get any passwords entered on the computer and send the passwords to the malware program creater or installer.

Malware can range in difficulty to remove. It may be very difficult to remove it or anti-virus programs may be able to remove it automatically.