AV-Test, the German security firm with which PC World partnered for this story, says that 70 to 100 new threats are discovered each day. Though many of them are variants of existing threats, waiting even a few hours for your antivirus software vendor to release fixes for them exposes your computer and others to harmful infection. Plus, viruses aren't the only problem. Virus writers are also sending worms--which don't need a host file in order to spread--and other destructive programs such as Trojan horses to users as e-mail attachments.
"The Bagle author likes to do this," says senior security researcher Joe Stewart of LURHQ, a company that provides security consulting and managed security services. Because of such dangers, it's important that your antivirus application be able to recognize and remove not only viruses but other types of threats as well.
(Read story: "The New Virus Fighters.")
