F-Secure Virus Descriptions : BootExe

There are two known variants of this virus, which is quite remarkable from a technical point of view. It is very small, and infects EXE files in a remarkable way - inserting itself in unused space between the file header and the actual start of the code. It also infects the DOS boot records of hard and floppy disks.

Disinfection of boot records is little complicated, because the virus does not save a copy of the original boot record. Cleaning can be done in the following way: Use a disk editor to edit the file system type in boot record - virus adds three garbage characters after the type (FAT16 or FAT12), replace these with spaces. You can do this with DOS debug like this:

        c:\>debug
        -l 100 2 0 1
        -e 13b "   "
        -w 100 2 0 1
        -q