PDF Spammers Get More Creative
Like everyone else, your organization has probably seen an increase in spam messages that contain attachments. Although initial efforts to curtail PDF attachment spam have had some limited success, those efforts only seem to have made the PDF spammers more creative in how they manage to get past ant-spam filters.
According to PC World, PDF spammers have found ways to get around email security by varying the content of the attached PDF files. Techniques have so far included altering the rendering size of PDFs, introducing pixel changes to make PDF blocking using signatures impossible, and adding random text within the PDF attachments.
Some PDF attachments are now also being encrypted, making it harder for anti-spam filters to detect their contents. The number and variety of techniques used suggest that bots were used to create the PDFs, and the intent was to create so many variations that anti-spam engines would be overwhelmed.
