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03 November 2006, 15:17

Spam makes a comeback

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The service provider MessageLabs has reported in its October report an increase in the proportion of email traffic made up of spam. By contrast the proportion of phishing and virus-infected emails fell back to homeopathic quantities. Spam now accounts for three quarters of all emails, an 8.5 per cent increase compared to the figure for September.

MessageLabs has identified the main cause of the new volume of spam as two pieces of malware which find their way onto victim's computers via email - SpamThru and Warezov (also known as Stration). SpamThru carries out its work with particular skill and cleans the prospective spam-dispersing zombie PC of other parasitic software using a hacked version of the Kaspersky virus scanner. This trojan is also equipped with a routine for individualising image spam by inserting random pixels, compressions and stretches so that outbreak and spam sensors are left with little chance of detecting similar emails using hash values.

The first variants of Warezov come to light in mid August this year. The trojan started appearing in large volumes exactly a week ago. What the two pieces of malware have in common is that they download and send new trojan variants from web servers - the changes mean that most virus scanners are unable to recognise the new variants. Recipient addresses and spam templates are also downloaded from servers over the internet, allowing them to send millions of hard-to-identify spam mails very rapidly.

A few months ago the proportion of email traffic made up of spam was decreasing. With SpamThru and Warezov the spam industry has made significant strides in circumventing spam protection mechanisms. Despite the mass distribution of these trojans, the number of virus-infected emails dropped by 0.12 per cent to precisely one per cent. The number of phishing mails fell by 0.06 per cent to 0.53 per cent of total email traffic in October.


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