MG stands for "Matematicheska Gimnazia", the name of the school in Varna in Bulgaria where the virus seems to have been written. MG hides itself in the upper half of the interrupt table, causing programs like Netware to crash. Several variants are known, and have been named MG-1, MG-2, etc.
Once detected, the F-Secure security product will automatically disinfect the suspect file by either deleting it or renaming it.
More information on scanning and removal options available in your F-Secure product can be found in the Help Center.
You may also refer to the Knowledge Base on the F-Secure Community site for more information.