Symantec is not the only security vendor that has had to deal with vulnerable antivirus software. But more in-the-wild exploits have leveraged Symantec's bugs than have attacked its rivals.

The Cupertino, Calif.-based company has even drawn expletive-laced tirades from hackers. In a blog entry a week ago, Symantec researcher Stephen Doherty wrote, "From time to time, virus writers leave messages in their code. Sometimes these are shout-outs to other virus writers, sometimes it is their own nickname, and other times they send messages to us. Here is one that speaks for itself.

"Dear Symantec: For years I have longed for just one thing, to make malware with just the right sting, you detected my creation and got my domains killed, but I will not stop, I can rebuild. ..."