In today's threatscape, antivirus software provides little piece of mind. In fact, antimalware scanners on the whole are horrifically inaccurate, especially with exploits less than 24 hours old. After all, malicious hackers and malware can change their tactics at will
. Swap a few bytes around, and a previously recognized malware program becomes unrecognizable.
To combat this, many antimalware programs monitor program behaviors, often called heuristics, to catch previously unrecognized malware. Other programs use virtualized environments, system monitoring, network traffic detection, and all of the above at once in order to be more accurate. And still they fail us on a regular basis.