Hello Ashoka,
You have provided very limited details.
Could you please provide us the file name and path of the file located on? If possible please provide us a screenshot.
Trojan.Gen is a generic detection for many individual but varied Trojans for which specific definitions have not been created. A generic detection is used because it protects against many Trojans that share similar characteristics.
Understanding the file location and file name may give us some idea to assist you with the Threat.
Secondly, is the name of the file starting from DWH***?
If yes, you may check the links provided by Chetan above.
I doubt this is the known issues. The issue of multiple DWH files being created and retained has been improved in SEP 11 Release Update 7 Maintenance Patch 2 (RU7 MP2) and SEP 12.1 RU1 MP1.
Check these Articles below:
When new virus definitions are in place and the quarantine is being scanned, a DWH file is created and detected by Auto-Protect
http://www.symantec.com/docs/TECH102953
DWH***.tmp files are detected in the user profile temp directory.
http://www.symantec.com/docs/TECH92399
Hope that helps!!