PDF Spam is largely considered to be the latest generation of image spam, which uses graphics instead of other masking techniques to conceal an unsolicited advertisement’s call to action. With PDF Spam, the images are embedded within attached .pdf documents instead of within the body copy of the message. Our Threat Department reports they are also seeing an increase in PDF Spam which uses text within the .pdf document instead of images.
- The nature of this situation is a constant arms race. The Spam Soap Threat Center is proactively monitoring, testing and developing sophisticated techniques to bring emerging spam threats under control.
- The Premium Anti Spam Multilanguage Filter (included in the Spam Soap Core Filtering Bundle) is effective at recognizing the signature of the PDF, its variants and is capturing a high percentage of the incoming spam.
- We can assume this new assault by spammers will continue to develop as recent estimates state total spam volume will increase 3 to 4 times in the coming months.
- The Heuristics and Bayesian filters used by Spam Soap can be used to hook into the accompanying message text, to recognize the existence of a PDF attachment, etc.
- PDF spam detected up to this point does not contain a virus payload, but our Threat Center anticipates this to appear in the near future.
- Due to the size of PDF spam messages, unprotected users can expect a significant increase in storage and bandwidth.
- PDF Spam has mostly contained images up to this point; however the most recent spam run actually contains text within the PDF body.
If customers do received such messages, they are urged not to open suspect messages or download .pdf files attached to unsolicited messages from unfamiliar senders.