Some of the groups I follow have been all gunked up lately by someone who appears to be casting a net for more zombies. The posts all claim to be various keygens, cracks, etc.
Here's a regex to put in your reject list
(?#hide trojans)(\b\d*crack\b)|(\b\d*key\b)|(keygen)|(keymaker)|(\b\w+\.exe\b)
Of course, if you run an exe you dl'ed from usenet, you deserve what you get - but it's irritating having the bogus posts there.
And if you really have to run something you dl'ed, do it in a VM. A virus scan is not going to protect you.