Along with the potential for more and varied criminal activity including cyber-extortion, spam today is increasingly made up of Word documents and images. A trend Sophos also identified on Monday.
This is bogging down the Internet as a whole and making corporate communication via email more and more expensive to manage and maintain.
Hackers now use techniques such as re-arranging as many as 25 tiny images into a message in an HTML email or using animated GIF attachments to bypass optical character recognition technology in an effort to bypass email security systems. Infected computers are now also re-trying temporarily blocked email connections just like real mail servers do.