From: bontchev@fbihh.informatik.uni-hamburg.de (Vesselin Bontchev)
Newsgroups: comp.virus
Subject: Re: Info on Commander Bomber and Starship? (PC)
Date: 16 Nov 92 14:08:56 GMT

tck@bend.ucsd.edu (Kevin Marcus) writes:

> Yeah, please post up a description.

The virus is a memory resident COM file infector. File size increases
by 4096 bytes. The installation check ("Are you there?") is INT
21h/AX=424Fh; if it returns 4D42h in AX, this means that the virus is
resident. The virus infects on file execution only; not on copying.
True Execs are intercepted (AX=4B00h), which means that no overlays
will be infected. The virus is not encrypted and contains two plain
text strings: "COMMANDER BOMBER WAS HERE" and "[DAME] [DAME]". The
"COMMAND" part of the first string is used to check the names of the
infected files - the virus refuses to infect a file, the name of which
begins like that. Therefore, the file COMMAND.COM will not be
infected. The virus does not infect files smaller than 5120 bytes. The
type of the file is checked (both MZ and ZM checks are performed) and
only true COM-type files are infected. The date and the time of the
infected files are preserved, but the attributes are not. The ReadOnly
attribute will not stop the virus from infecting the file, although it
will remain turned off after the infection.

Well, essentially, this is all. All of the viral code, that is. It
occupies about 560 bytes. The remaining is code aimed to conceal the
virus entry point. The virus can reside anywhere in the COM file.
Furthermore, it consists of about a dozen tiny parts and one main
body. The tiny parts do essentially nothing - just a few insignificant
instructions and then transfer control to the next part. The
generation of these parts is very polymorphic; meaning that they can
be -very- different from one infected file to another. The main part
is not even encrypted, which means that it can be detected with a
simple (even not a wildcard) scan string, but in order to do this, the
scanner must scan the -whole- file (which slows down the scanning
considerably). Smart tricks like scanning at the file entry point, or
at the beginning and at the end of the file only, do not work with
this virus.

The second string found in the virus suggests that Dark Avenger
(because he is the author of this Commander Bomber virus) intends to
combine it with the MtE polymorphic mechanism for variable encryption.
Detecting MtE with a scanner now is a nightmare, even if you know that
the file entry point points to it. Detecting an MtE-based virus with
the MtE-generated decryptor which can reside just anywhere in the file
will be a double nightmare, if you care not to produce any false
positives... Fortunately, it is not so easy thing to do...

It is is obvious that the Commander Bomber virus is yet another
"demonstration" virus, like Dedicated. It is an attempt to show that
known-virus scanners can be made obsolete. It is also a buggy virus -
due to some reasons (not clear to me yet), the virus crashes after
some infections. Other than that, there is no destructive payload in
it (or any other payload for that matter).

Regards,
Vesselin
- -- 
Vesselin Vladimirov Bontchev          Virus Test Center, University of Hamburg
Tel.:+49-40-54715-224, Fax: +49-40-54715-226      Fachbereich Informatik - AGN
< PGP 2.0 public key available on request. > Vogt-Koelln-Strasse 30, rm. 107 C
e-mail: bontchev@fbihh.informatik.uni-hamburg.de    D-2000 Hamburg 54, Germany