Global spam has increased nearly 100 percent year on year according to statistics from IronPort Threat Operation Center. Image-based spam is becoming a more prevalent form of spam because it defeats older, simpler spam-classifying engines. IronPort: 25 percent of this spam was image-based compared to 4.8 percent the year before. Image spam contributed to more than 819 terabytes of bandwidth per day during 2006. The average message size also increased from 8.9 kilobytes to 13 kilobtes.”]
Source: https://www.csoonline.com/article/2120847/image-spam-on-the-rise–says-ironport.html