| position | virus | percentage by occurrence |
|---|---|---|
| 1 | I-Worm.BadtransII | 40.8% |
| 2 | I-Worm.Sircam | 15.6% |
| 3 | I-Worm.Hybris | 6.4% |
| 4 | I-Worm.Aliz | 3.1% |
| 5 | I-Worm.Nimda | 2.7% |
| 6 | I-Worm.Magistr | 2.3% |
| 7 | Trojan.PSW.GIP | 2.0% |
| 8 | I-Worm.Happytime | 0.5% |
| 9 | JS.Trojan.Seeker | 0.4% |
| 10 | I-Worm.Klez | 0.3% |



September – December 2001 Top Ten