Hello,
Have you created a Case with Symantec Technical Support?? It is adviced to create a case.
I would advise you to upload this suspicious file to the Symantec Security Response Team on -
https://submit.symantec.com/essential
OR
http://www.threatexpert.com
Secondly in your case, it is advisable to follow few important steps:
1) Make sure all these machines are Patched with ALL Latest MS security patches and service packs.
2) Make sure the machines are installed with the Latest Symantec virus definitions.
3) Disable the Autorun Feature on the machine.
Preventing a virus from using the AutoRun feature to spread itself
http://www.symantec.com/business/support/index?page=content&id=TECH104447
Later, incase of suspicious activity still happening, then follow the steps provided in the Article below:
Using Symantec Help (SymHelp) Tool, how do we Collect the Suspicious Files and Submit the same to Symantec Security Response Team.
Here's some advice from Security Response on how to make the best use of SEP. Auto-Protect with traditional AV derfinitions alone is not enough for a complete defence against today's sophisticated threats: using IPS, Insight etc is crucial. And, of course, educated users following best security practice... that';s the best protection.
http://www.symantec.com/theme.jsp?themeid=stopping_malware&depthpath=0
Hope that helps!!