Spam Filters has been challenged by Turing Test
According to the news by The Register on July 6, 2007, the head of an anti-spam software developer said that the spammers had turned an anti spam trick into a fuzzy and confusing text to their advantage, which even the system can't identify.
The destroyed text images have appeared in PDF files promoting German penny-stocks, which come in yet a new iteration of 'pump & dump' scam.
The difference in this kind of spam is that they are PDFs that makes it more difficult to filter. Moreover, the content of the message is heavily destroyed so that the system cannot recognize it.
This kind of PDF files that attach spam emails came out in June 2007. Further, the experts have already warned the users that the latest spam technique attaches PDF files to emails in order to cheat the users, as per the news by CRN.com in fourth week of June 2007.
As per the email security vendors, Marshall, spammers have shifted their devices from image spam to PDF attached email. They claim that after finding ways of fooling spam filters, they are now looking for new methods to send their messages across by the help of PDF attached spam mails.
Neil Crook, European technology-chief at 'Cloud mark', an anti-spam firm, termed it as "a sort of Turing-test for spam filters".
According to The Register, Crook added that they have noticed various PDF stock spam emails around the last ten days, and there's one more spike on the night of July 5. He said that the images are comparatively easy for humans to identify, but it proves to be quite the reverse for the computer.
Crook said that the spammers had used the same method, which the websites uses for keeping spammers away by making the visitors key in destroyed text at the time of registration, as per the news by The Register.
Almost 75,000 zombie computers distributed the PDF files outbreak, which accounted to be 9% of the total email traffic, making it one of the 10 largest outbreaks of 2007. US, Germany and Spain are the top 3 locations of these zombies and the recipients were mainly the residents of Europe.
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» SPAMfighter News - 19-07-2007