Whether you clicked on a misleading banner ad, opened a file sent by a Nigerian prince or simply downloaded the wrong porn, everyone's dealt with a computer virus at some point. While bad programming or virus checking software contains most outbreaks, some malware has managed to reach pandemic levels. With the help of Golden Richard III, a professor of computer science at the University of New Orleans and an expert on computer viruses, Popsci.com takes a look at ten viruses, worms and Trojans that reached levels of digital plague.

10. Creeper

9. Elk Cloner

8. The Morris Worm

7. ILOVEYOU

6. Code Red

5. Nimda

4. Slammer

3. Blaster

2. Welchia
