The Mytob.c worm remained the top malicious program of the month accounting for nearly one-third (32.97 percent) of all viruses, according to the Kaspersky Lab.
NetSky.t ranked second in the study with nearly 11 percent of recorded malware, and the LovGate.w virus was third with more than nine percent, according to Kaspersky.
Four of the top ten - and ten of the top 20 - were Mytob variants. The lab noted in a news release that Bagle.fj, which reached sixth place in February, was the most noticeable virus that failed to reach the top 20. Zafi.d, the list's leader in January 2005, dropped nine places on this month's list.
Kaspersky also reported that the top ten viruses increased activity in March, while noting that malware activity was slower than during February.
Meanwhile, the Zafi-B virus took first place in Sophos's list of this month's top teen viruses, with more than 17 percent of recorded malware. Netsky-P was in second place with more than 15 percent, while Nyxem-D was the third-most-seen virus of the month as nearly 8 percent of all malware.
Sophos also noticed that Clagger-I, a trojan that placed sixth on the company top ten, was in the poll for a second consecutive month.
The firm reported that 0.9 percent of all emails were viral during the month.
"At this point one would think that computer users would have gotten the message, but it obviously bears repeating: treat unsolicited email attachments with extreme caution," said Ron O'Brien, senior security analyst at Sophos, which has U.S. headquarters in Lynnfield, Mass. "Cybercriminals prey on the naïve and unsuspecting, and getting infected by malware means you are at risk of getting ripped off."