Anti-virus programs (at least the ones civilians have access to) have a security value that approaches zero in regards to preventing you from being entirely pwnt by any attacker who targets you. They exist entirely to prevent you from being pwnt by a dragnet attacker who isn't targeting you in specific, and they even do a poor job at that. All anti virus scanners really do is prevent botherders from getting twenty million node botnets (instead they might get only a few hundred thousand before the virus is detected and the anti virus product can prevent it from infecting you). In short, anti virus program protects you if you are insanely shitty at computer security an launch random attachments etc, and they protect you from being the 1,000,000th infected node (of course they don't protect you if you are one of the 1,000,000 infected nodes). Anti virus programs give you an almost entirely false sense of security. I still suggest them for windows users, but if your security is coming from anti-virus scanners you are pretty much insanely fucked and not at all secure.