The Microsoft Malware Protection Center (MMPC) malware naming standard is derived from the Computer Antivirus Research Organization (CARO) Malware Naming Scheme, originally published in1991 and revised in 2002. Most security vendors use naming conventions based on the CARO scheme, with minor variations, although family and variant names for the same threat can differ between vendors. A threat name can contain some or all of the components seen here:

Informative read at Microsoft.