GenCRCDiff.exe is an executable file used by Trend Micro Worry-Free Business Security 6.0 (WFBS 6.0). It’s part of the SmartScan server technology that allows Trend to distribute smaller pattern files to the client machines rather than the larger full size pattern files. To do this, it downloads a file from Trend Micro servers and then runs this GenCRCDiff process to massage it into the pattern file for distribution to your client machines. During this process it consumes both CPU and Disk resources. Trend have documented this here along with a mechanism to limit the amount of CPU used. This process only runs hourly to handle the creation of the diff files. It is not running continuously and therefore you won’t see it in the task manager unless it’s actively processing a file at that moment in time.
Furthermore, you will only see it running on WFBS 6.0 before Service Pack 2 (SP2) and if you disable the SmartScan server component of WFBS 6.0, then you will not see this process running at all.
In WFBS 6.0 SP2, Trend have changed the default processing of the diff files to use their servers in the cloud. This should mean that you do not see this process running at all on a server that has SP2 installed on it.