Rising email security threat
ConvergenceAsia staff
14/08/2007

Data collected by SonicWALL showed that there is an ongoing growth in the volume of spam, virus and phishing attacks, increased use of PDF spam and the emergence of a new wave of Excel and Zip spam.

The data were collected from its Smart Network database of over 1.3 million email users. The results were based on aggregated results from the SonicWALL Smart Network from April to July, 2007.

SonicWALL's analysis shows that Directory Harvest Attacks (DHA), Denial of Service (DoS) and similar attacks decreased by 2 per cent over the quarter, but still accounted for 55.7 per cent of email flowing into inboxes. Spam, viruses and phishing attacks, increased by 4 per cent from Q1 2007, and comprised 37.4 per cent of all email, with the remaining 6.9 per cent being good email – a 3 per cent increase over Q1 2007.

During the second quarter of 2007, PDF spam emerged as a persistent threat. These types of email attacks typically contain little to no text in the body but attach a PDF file, usually a stock or drug spam message containing malicious code, which, if opened, can be automatically downloaded onto a victim’s computer. SonicWALL believes the widespread adoption of PDF spam illustrates the adaptability of spammers in finding new techniques to counteract image spam prevention techniques.

"PDF spam demonstrates the continued innovation in spam techniques that attempt to bypass anti-spam detection and trick employees into opening emails that give the appearance of legitimate business letters," said Andrew Klein, senior product manager for SonicWALL's Email Security division. "PDF spam is effective because files in PDF format have long been considered an acceptable way for businesses to transfer information. Much like phishing emails, spammers have manipulated the trust factor to get past both technical and psychological defenses."

More recently, SonicWALL has detected an increasing amount of Excel and ZIP file spam. Utilising the same trust-busting premise as PDF spam, Excel and ZIP spam succeed because they mimic legitimate correspondence to get more eyes to view the message.

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