it is not the MCS file. You can take a look into the file, there you can see the detection name. The file should be in cleartext.
If you have the extra.dat file you can also add it manually to your system.
On EPO you will find the file here: ?:\Program Files (x86)\McAfee\ePolicy Orchestrator\DB\Software\Current\EXTRADAT1000\ExtraDAT\0000\