The kickers are that it's both easy to launch the exploit and particularly vicious in most cases. As Symantec is intercepting system input and output, you only need to email a file -- the victim doesn't even need to read the email, just the act of AV scanning it is a trigger -- or send a web link to wreck someone's day. And on Windows, an attack compromises the kernel -- you know, the very deepest level of the operating system.

The good news? Symantec is taking care of this relatively quickly. Its antivirus suites with LiveUpdate should already have a patch in place. The biggest concern surrounds software that requires a more conventional patching process. There aren't any known exploits in the wild, but it's reasonable to presume that Symantec wants to have everything up to date before would-be hackers develop an intrusion technique.