[wmt]

How much more? I always imagined that it's more likely for a standard user to open every email attachment and execute it than it is to get targeted by a malicious attacker who knows what software your users are running and writes exploits tailored for them, but I could be wrong.

[djrogers]

No tailoring required with something like this since it's worm-ready; blast out a ton of emails to seed the worm, then post exploit the worm emails itself to everyone in your address book. It won't take too long before a significant portion of the vulnerable systems win the world are infected.

See Blaster, Slammer, CodeRed for historical examples....