Programs to detect and remove computer viruses. The simplest kind scans executable files and boot blocks for a list of known viruses. Others are constantly active, attempting to detect the actions of general classes of viruses. antivirus software should always include a regular update service allowing it to keep up with the latest viruses as they are released.
Basically, the malware presents itself as a piece of antivirus software that is going to protect your machine.
And most users don't need to install things like antivirus software that's almost a necessity on Windows.