If there are any admins for this site, check out this link:
http://www.vbulletin.com/forum/showthread.php?t=211647
These posts aren't actually made by 'people' but by 'bots'. I have some forums too but they run on a different system. We have the same problem and I have gradually got used to stopping them.
entwisi is also correct. Moderating the forums will not enable you to get the virus, but visiting the links would have. Be careful whenever someone new posts links. If you think it is a spam bot, check the email address they registered with. That usually gives it away.