Image Spam still increasing

During the last week image spam accounted for up to 40% of the total spam received, compared to about 1% a year ago. Image spam has been significantly increasing for the last few months and various kinds of spam, typically pump and dump stocks, pharmacy and degree spam, are now sent as images rather than text. Image spam is typically three times the size of text based spam, so this represents a significant increase in the bandwidth used by spam messages.

During this period our image spam detection remained well over 99% and image spam discard rates were almost as high, averaging about 95% of image spam discarded. Spammers moved to image based spam in an attempt to evade detection, but its not working!