SurfControl Filter for SMTP v4.6 filtering technology can be easily bypassed when more than 16 zip files are nested inside of a zip file. The filter only scans the first 15 files inside of a zip file, therefore allowing malicious files through.
You can download this advisory from the following link: https://packetstormsecurity.com/files/download/31405/surfcontrolsmtp46.html
Source: https://packetstormsecurity.com/files/31405/surfcontrolsmtp46.html.html