[B][I]
Well, a nuker isn't gonna do much more then knock you off-line, although most nukers don't work anyway, heh.
Mail bombs will just piss you off and screw up your e-mail server, but I don't see them doing any real damage.
The only sorta things that can really nail you are virii...the more insidious kind can really trash your files and even muck up your HD to the point of no return...
Thus, best tips would be don't download anything questionable, go get a good virii scanner, and make sure you have back-up disks.
hope this helps
-Grim