Unless you know their utility, unless you are sure of their source and are convinced that the sender applies reliable security measures, do not accept such disks and destroy program files attached to e-mails. If you have no other choice but to accept them, detach them and scan them with the lastest update of your anti-virus software prior to executing them.
CodeRed et Nimda sont deux exemples de vers informatiques touchant particulièrement les serveurs Web.