I believe it depends on what you purchased. According to the 6.7.2 manual, IM can run Sophos, Authentium and/or McAfee AV. If you paid for Authentium and don't have it, then I'd follow up with your reseller about the license. If you go to System > License Manager, it should show what anti-virus product(s) you are licensed for and when they expire. I hope that helps.
many thanks for your response.
i checked the license list from the appliance and it seems that we paid only for the McAfee Anti-Virus.