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Image spam

(also image-based spam)

Image spam definition

Image spam is a spamming technique in which textual spam messages are embedded into images attached to the email. By embedding these messages, spammers attempt to get around spam filters that typically scan for particular keywords. This technique works because many anti-spam systems can’t read images.

How image spamming works

  • Spam messages were traditionally sent as text, which is what traditional spam-blocking software is designed to block.
  • Most spam filters (like SpamAssassin, Bogofilter, RadicalSpam, or SpamBayes) perform textual analysis and search for certain spam keywords.
  • Instead of sending a spam message in text format, spammers place the text inside the image to bypass the spam-blocking software.
  • The spammer successfully delivers the message to the user’s inbox.
  • The spam message is conveyed when the user opens the email (without opening the attachments).

How to block image spam

  • OCR programs. Optical character recognition programs are software designed to scan and analyze text and images. The main drawback of OCR programs is that they require a lot of bandwidth and can max out your CPU (central processing unit). OCR programs are also incapable of reading handwritten messages.
  • Delete the messages. The other way to avoid image spam is to monitor the messages in your inbox and delete them without opening them. This method requires careful monitoring because spammers can make spam messages look like emails from someone you know or another legitimate source.