As has already been mentioned, all software has bugs, and as it gets steadily more complex and interwoven I would expect vulnerabilities to correspondingly increase. However, something like antivirus is not a solution. It should be part of a managed risk reduction, which starts about a metre away from the screen! If you're on any kind network your security boundary should include a decent firewall there, not inside the computer. Stop most of the buggers at your garden gate, not the back door.
It wasn't me!
(Well, actually, it probably was)