Threat Description

BootExe

Details

Aliases: BootExe, BootExe, BFD
Category: Malware
Type:
Platform: W32

Summary



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

(If you are not familiar with debug or disk editor, it might be a better idea to call F-Secure anti-virus support instead.) After this, issue the command SYS C: from a clean diskette with the same version of DOS than is on the hard disk.

Contact your local F-Secure support if you need further instructions. F-Secure anti-virus products will disinfect the EXE files infected by this virus.



Removal



Automatic Disinfection

Allow F-Secure Anti-Virus to disinfect the relevant files.

For more general information on disinfection, please see Removal Instructions.








Description Created: Mikko Hypponen, F-Secure


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