image spam


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image spam

An email advertisement in the form of an image in the message rather than text in order to avoid detection as spam. Spam filters typically analyze words in a message, which is relatively fast, but scanning images with optical character recognition (OCR) to extract the text is slow. In addition, spammers have already circumvented optical scanning by fracturing the text within the image similar to the CAPTCHAs on Web page forms (see CAPTCHA). Animated GIFs are also used to spread the text across multiple frames, making it harder to analyze.

Message Fingerprinting
Another defense is to track known image spam and save the attributes of their text and images as signatures that can be quickly analyzed. In many cases, the fingerprint need only be of the image. Although this is a faster detection approach, keeping up with the latest image spam signatures is like keeping virus signatures up-to-date. See spam and OCR.


Not Exactly Clear
Many spam images are legible to a human, but this one from Korea-based CLC Holding Company is barely readable. Images such as this are sent because spammers are counting on the one person in 10,000 who will actually take the time to decipher it.
References in periodicals archive ?
Text-based spam still appeals to automated scripts for word scrambling, rephrasing or (synonymic) substitution, while image spam usually deploys obfuscated content.
Barracuda Networks Inc, a provider of spam firewall solutions, announced on Thursday (22 February) the availability of its third generation of image spam defence enhancements to the Barracuda Spam Firewall.
Barracuda has reportedly seen a more than 67% increase in overall spam volume and a 500% increase in image spam since August 2006.
This meant that Mail-Secure users experienced zero degradation with no false positives from the very first PDF image spam attacks.
Despite the arrest of Robert Soloway, also called 'Spam King', and claims that image spam is on the decrease, the company does not believe that spam levels will drop significantly soon.
Incidentally, these spammer worms leverage the latest mass-mailing technique: image spam. In 2006, in order to bypass spam filters, spammers revived an old trick that has now become quite common: placing email advertising text within an image, and scattering random elements such as dots or lines throughout the text.
Adaptive Image Filtering (AIF) technology has been introduced by Tumbleweed Communications Corp (Tumbleweed) (Nasdaq:TMWD), a provider of messaging security solutions, intended to fight the growing volume of image spam.
This reduces a lot of the horsepower problems associated with processing image spam. Nevertheless ISPs are investing in more filtering equipment simply to keep pace with the rising tide of spare.
Overall, image spam has increased from 1% a year ago, to up to 25% this week.
Anti-spam vendors like Barracuda Networks have been extremely successful at creating fingerprints for this type of image spam. This reduces a lot of the horsepower problems associated with processing image spam.