Hello,
Worm Win32.VBNA.b is a network-aware worm infection, which is also regarded by many experts as cloaked malware.
http://www.symantec.com/security_response/attacksignatures/detail.jsp?asid=24580
In your case, I would suggest the below Plan of Action:
1) Make sure ALL Computers are installed with Symantec EP with latest / updated with virus defintions.
2) Install ALL Latest Microsoft Secuirty Patches / Sevice Packs on ALL machines.
3) Make sure ALL the client machines are using the Latest Vendor Patches installed.
4) Disable Auto play with GPO
http://support.microsoft.com/kb/953252
5) Disable the System Restore with GPO
http://support.microsoft.com/kb/283073
6) Disable Scheduled Tasks with GPO
http://support.microsoft.com/kb/310208
7) Enable Security Auditing with GPO
http://support.microsoft.com/kb/300549
8) Incase of any shared / mapped drives present, make sure these are password protected.
9) Scan ALL the machines...
In case of a Suspicious file, zip the container Folder and when you open the zipped folder, you may see the Threat file in it.
Submit the .zip folder to Symantec Security Response Team on
https://submit.symantec.com/websubmit/essential.cgi
We also offer a self-service site to analyze files, at http://www.threatexpert.com, which can give you more information on the files you submit to it.
Also, check these Articles:
Using Symantec Support Tool, how do we Collect the Suspicious Files and Submit the same to Symantec Security Response Team.
https://www-secure.symantec.com/connect/articles/using-symantec-support-tool-how-do-we-collect-suspicious-files-and-submit-same-symantec-sec
Scanning a file with a competitor's antivirus program detects a virus, but scanning with Symantec AntiVirus or Symantec Endpoint Protection does not
http://www.symantec.com/business/support/index?page=content&id=TECH98929
Hope that helps!!