S-Bug is a highly polymorphic virus that has been reported to be in the wild in USA and in several other locations.
Virus stays resident in memory occupying 9 KB's of DOS memory. It hooks the following INT 21h functions: 3Dh, 4Bh, and 6Ch. Infected files grow in size between 4k and 5k bytes.
Infected EXE and overlay files may fail to execute correctly. Virus includes string "Satan Bug virus - Little Loc".
The virus will only become resident if the environment variable COMSPEC= is set to point to a file called COMMAND.COM.
S-Bug virus also removes validation codes added to files by McAfee SCAN and CPAV's Immunize function.
Depending on the settings of your F-Secure security product, it will either automatically delete, quarantine or rename the suspect file, or ask you for a desired action.
More information on the 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.
A related variant. Uses similar encryption, but the actual virus is simpler and non-resident.