Satan Bug Natas virus information

Satan Bug Natas, or S_Bug, is a highly polymorphic virus that was in the wild in USA and in other locations. The virus stays resident in memory occupying 9 KB of DOS memory. It hooks the following Int 21h functions: 3Dh, 4Bh, and 6Ch. Infected files grow between 4 k and 5 k bytes. Infected EXE and overlay files may fail to execute correctly. Virus includes string Satan Bug virus - Little Loc. The virus only becomes 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.