Critical System Protection

I have a customer running Norton Internet Security 2014. They were informed by the local ISP that a government agency had alerted the ISP that this customer was infected by a dangerous piece of malware, "Game Over Zeus." My customer called me in a panic. The first thing I did was to run a full system scan with Norton Internet Security...the end result showing only 41 tracking cookies! ...no significant malware. I then installed Malwarebytes whose scan found 13 instances of Trojan.gen and Trojan.Zbot and removed the malware. I always tell my customers that Norton Internet Security is number one for blocking and removing malware. I am now concerned about how this infection could have slid past NIS. Can anyone enlighten me about this?

NIS obviously didn't have a signature to find this. Best thing you could do is submit the file for review and scan with a third party removal tool.

Other thing you may want to do is post on the Norton forums for best visibility Http://community.norton.com

Thanks  _Brian, I have posted to the Norrton forum as you suggested. I thoiught NIS used a heuristic approach as well as signature recognition.