The number of spam messages containing malicious attachments rocketed in the most recent quarter, despite overall spam levels falling, according to the latest research from Kaspersky Lab.
The security vendor's quarterly spam report found that malicious spam doubled during the third quarter, averaging 4.6 per cent compared to 1.9 per cent in the previous three months.
The percentage of malicious attachments in email traffic reached an unprecedented high of 6.3 per cent at the start of the third quarter, said Kaspersky Lab.
Most of the spam appears to have come in the form of fake notifications from online stores or services such as Twitter, Facebook and Windows Live.
Following the links will download Bredolab backdoor malware onto the victim's PC, which in turn enables the downloading of other Trojans.
"The increase in the volume and quality of mass malicious mailings confirms that spammers and cyber criminals have started acting in unison to create complex infection strategies, which include connecting a victim computer to a botnet, sending out spam, stealing personal information and so on," said Darya Gudkova, head of content analysis and research at Kaspersky Lab.
Overall, spam fell 1.5 per cent to 82.3 per cent of all email, in large part owing to the closure of more than 20 control centres used by the prolific Pushdo/Cutwail botnet, which is responsible for some 10 per cent of the world's spam, said Kaspersky Lab.
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