Two highly active botnets have pushed spam levels up by five per cent this month, according to security firm Symantec.
The company's MessageLabs branch, now called Symantec Hosted Services, said in a new report that spam accounted for 89.4 per cent of email traffic in February, an increase of 5.5 per cent over last month.
Much of the gain was attributed to a 51 per cent increase in spam activity from the Grum botnet, making it accountable for more than a quarter of all spam.
The Rustock botnet was also blamed for the increase in junk mail. MessageLabs said that the botnet sprang to life on February 17 with a huge pharmaceutical spam run that boosted daily spam levels by 25 per cent.
"Whether the spammers are trying to clear this spam run more quickly, or have discovered that it is successful, they have certainly been using multiple botnets to distribute high-volume spam campaigns in February," said Paul Wood, Symantec Hosted Services senior intelligence analyst.
"Based on these latest spam patterns, we can predict additional surges in spam in the coming weeks."
There was some good news, however. Instances of malware-laden spam messages rose by just 0.02 per cent, despite the climb in overall spam levels, while instances of phishing spam rose just 0.04 per cent.