Sophos ranked the Netsky-P virus as last month's top virus, collecting nearly 14 percent of all reports. It displaced January's top virus, Sober-Z, which stopped spreading on Jan, 6. Netsky-P was first detected in March 2004.
Sophos' runner up for February was the Nyxem-D virus, known to many PC users as the Kama Sutra Worm. The virus spread via spam email disguised as sexually explicit material.
However, analysts from Sophos were most surprised by the entry of the Clagger-G trojan into the No. 8 spot. The high number of reports of a trojan is evidence of mass spamming of financially motivated malware, they said.
"In order for this Clagger trojan to make an appearance in the top ten, it must have been spammed out to millions and millions of email addresses worldwide," said Carole Theriault, senior security consultant at Sophos. "Trojan horses, which cannot spread on their own, account for roughly two-thirds or all reported malware. Rather than mass bombardment, most trojan creators focus on small targeted groups to pilfer cash and sensitive information."
The Bagle-Zip virus reentered the list at No. 3, while Zafi-B and Mytob-FO rounded out the top five.
The company's research showed that more than 1 percent of emails is viral, and 119,192 email threats are in the wild.
Ron O'Brien, Sophos senior security analyst, said the findings are more proof of the financial motivations of today's malicious users.
"As the threats increase by the minute, computer users and businesses worldwide must make a concerted effort to fully protect their computers and networks," he said. "Today's cybercriminal is increasingly financially motivated and is proving to be adept at comprehensive attacks integrating malware and spam technology."
Meanwhile, the Mytob.c worm was the Kaspersky Lab's top ranked virus of February, maintaining nearly 34 percent of all reported virus activity.
It was followed by LovGate.w, Zafi.d, NetSky.t and NetSky.b in the top five rankings.
Bagle.fj, at No. 6, and NetSky.q, at No. 9, were the only other two non-Mytob viruses in the Kaspersky top ten.
Over all, Kaspersky called last month "superficially far more peaceful than January, a month that brought considerable media coverage for the Nyxem.e and Feebs epidemics."Shane Coursen, senior technology consultant at Kaspersky, said "there wasn't a lot of issues during the month of February." "There is usually a lull in virus writing around these months," he said. "Around April, we usually start to see them get going again, but we don't know for sure."
Kaspersky, however, called the Bagle.fj worm the virus that disturbed PC users most in February.
"Bagle.fj was spammed to millions of email addresses on Feb. 2 and over the course of the next few days because the most common worm in mail traffic," Kaspersky said on its website. "Although currently the worm's activity is abating, the risk of infection remains high."