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Massive growth of malicious spam

18 August 2011

While several reports show that the global levels of spam have seen a steady decline over the past year, this month has seen a spike in the number of spam messages with malicious attachments, security firm M86 reports.

Using well-known tricks to deceive users, including subject lines about stolen credit cards, sent parcels and invoices, 13% of spam this month contained a malicious attachment. Yesterday, as many as one in four spam messages had malware attached to it. This means the volume of malicious emails is six times as high as during the previous peak in April, and twice as high as in September last year, just before the takedown of the Spamit affiliate program.

Researchers at M86 linked at least four of the current campaigns to the 'Cutwail' botnet. The file attached to these messages is a trojan downloader that downloads fake AV, SpyEye and a copy of Cutwail itself. With botherders suffering increasingly from takedowns of their botnets, it looks like they are also increasing their efforts to build and grow these rogue networks.

Using the VBSpam setup, where more than 20 anti-spam solutions are set up to filter real-time spam, we could see that the vast majority of these messages were being blocked by spam filters. Still, the average delivery rate of the malicious spam campaigns was 50% higher than that of all spam sent during the same period.

It should be noted that many products did not scan emails for malware, and the VBSpam set-up does not require them to do so - when combined with an anti-malware solution, delivery rates are likely to be lower. Nevertheless, it shows the importance, for home users and enterprise users alike, of running both anti-spam and anti-virus software.

More at M86's blog here.

Source: Virus Bulletin