Viruses and instant messenger attacks both decreased during February, according to message security firm Postini. But spam and encryption volumes rose during the month.
Postini said it processed over 22 billion emails last month. The company said it blocked 14 billion of them, and found that spam comprised 4 billion of that number, an increase of 2 percent since January.
The biggest spamming day of the month was Feb. 18, when 150 million messages were quarantined, the company said on Monday.
Inbound TLS encryption volumes also increased, from 6.5 percent of legitimate inbound traffic in January to 7 percent last month. Outbound encrypted messages grew from 1.5 percent to 3 percent during the month.
Viruses, however, moved in the opposite direction, falling back to their normal level of 1.5 percent of all email in February after a stormy January.
The top five viruses of the month, according to Postini, were mytob, bagle, NetSky, bank fraud and phishing viruses and Swen. Mytob was blocked by the company more than 18.3 million times.
Phishing volumes were also down from January, falling 65 percent from its mark two months ago.
Andrew Lochart, senior director of marketing for Postini, said many spam emails are offering to make consumers' dealings with the Internal Revenue Service easier.
"The increase I spam was due to an increase in tax preparation offers and other financial service offerings that are more prevalent as we approach April 15," he said.
Sophos had ranked NetSky as its top virus of February, while Kaspersky Lab also ranked mytob as its most widespread virus of the month.