Vote for Panda Security for ISA Servers
Panda Security for ISA Servers protects against all malware (viruses, worms, Trojans, spyware and adware, spam and hoaxes, phishing, dialers, hacking tools, security risks, etc.). It scans all file formats sent and received. It does this using a Web filter (ISAPI) and an application filter through HTTP, SMTP and FTP (over HTTP).