So what can an IT manager do to fight image spam? Surprisingly, most vendors are happy to say that existing technology is up to the challenge. For any employee accessing their email on a mobile device, where every kilobyte downloaded costs the company money and slows down the device, image spam poses an even greater inconvenience. Since text-based spam tends to be less than 5k, while the image-based type ranges from 5k to 40k and beyond, a single image-based piece of spam can have all the effects on systems of eight regular pieces of spam. Whatever proportion it does represent, image spam is among the most likely kinds of spam to get through filters, and it poses the same problems as its conventional cousin: it wastes employee time takes up bandwidth, processing power and space on email servers, their back-up systems and end-user systems and can pose legal issues if staff who receive it object to it. If a spam measurement is taken during a burst, it may appear that the percentage of this kind of attack is higher than it actually is. However, image spam campaigns arrive in bursts, he added, since they are sent via botnets controlled by spammers in the hope that some emails will beat the spam filters before they have time to adapt. "Some vendors put the figure at close to two thirds of spam, but that's scaremongering." "It's approximately ten to 20 per cent," said Mark Sunner, chief security analyst at email services company MessageLabs. Other commentators dismiss those figures as hype. Security vendor Marshal puts the figure as high as 56 per cent of all spam SurfControl says between 25 and 40 per cent is more likely while F-Secure and Sophos think that the proportion is around 35 per cent. Given these advantages, it is no surprise that image spam now comprises a considerable proportion of total spam traffic. Rather than using a simple text-based email, these spammers have embedded their kind offers into images, making it seemingly impossible for a standard spam filter to pick up the usual keywords that reveal the messages' true intents. Need pain releif (sic)? Some Cialis, perhaps? Or maybe you'd like to invest in China YouTV Corp (CYTV)? You've probably received at least a few emails offering some of these things because they managed to sneak past your spam filters.
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