Sober-Z topped the charts once again, despite a fix being available since November. Netsky-P made it back to number two, despite a cure being available for nearly two years, and Zafi-B, first detected in June 2004, has made a comeback at number three.
"Some of these worms have been around for years, and should act as a wake up call for businesses and users who don't have adequate protection," said Carole Theriault, senior security consultant at Sophos.
"These worms are simple to control as long as a consolidated solution is in place, and their spread would have been halted if antivirus updates were applied."
Sophos found 2,312 new viruses last month, and its research showed that one in 70 emails contains a virus.
The Sophos top 10 viruses in January 2006 cane be seen here.
NASA's Voyager 2 probe set to reveal secrets of space beyond the heliosphere as it goes interstellar
The probe is now more than 18 billion kilometres from Earth, with equipment enabling it to reveal some of the secrets of interstellar space
Four glaciers located west of massive Totten glacier have lost almost three metres of ice in height since 2008
Ceres, located in the asteroid belt, has a carbonaceous-rich upper crust, SwRI study claims
The spacecraft found traces of hydrogen and oxygen molecules, known as hydroxyls, embedded in the rocky surface of the asteroid