| Abstract |
This document describes how to write parasitic file viruses infecting ELF executables on Linux/i386. Though it contains a lot of source code, no actual virus is included. Measurement is the foundation of science. Unfinished snapshot taken on 2002-03-15. I predict that today will be remembered until tomorrow. |
In the tradition of release early, release often this document escaped version control at an immature stage. General direction and structure is not yet fixed. Big changes are likely. You might want to look at the discussion on LDP-discuss. For the time being you will find complete source of this release and all previous versions here.
Writing a program that inserts code into another program file is one thing. Writing that program so that it can be injected itself is a very different art. Although this document shows a lot of code and technique, it is far from being a "Construction Kit For Dummies". Instead I'll try to show how things work. Translation of infecting code to assembly is left as a (non-trivial) exercise to the reader.
An astonishing number of people think that viruses require secret black magic. Here you will find simple code that patches other executables. But since regular users can't overwrite system files (we are talking about serious operating systems here) that is not even half the journey. To make any impact you need root permissions. Either by tricking the super user to run your virus, or combining it with a root-exploit. And since all popular distributions come with checksum mechanisms, a single command can detect any modification. Unless you implement kernel-level stealth functionality…
I do believe that free software is superior, at least in regard to security. And I strongly oppose the argument that Linux viruses will flourish once it reaches a critical mass of popularity. On the contrary I question the credibility of people whose income relies on widespread use of ridiculously insecure operating systems.
This document is my way to fight the FUD. Use the information presented here in any way you like. I bet that Linux will only grow stronger.
All sections titled "Output" are real product of source code and shell scripts included in this document. Most numbers and calculations are processed by a perl-script parsing these output files. The document itself is written in DocBook, a SGML document type definition. Conversion to HTML is the last step of a Makefile that builds and runs all examples.
I used an installation of RedHat 7.2 for development All required tools are contained on the two freely downloadable CDs .
This document is copyrighted (c) 2002 Alexander Bartolich and is distributed under the terms of the Linux Documentation Project (LDP) license, stated below.
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In short, we wish to promote dissemination of this information through as many channels as possible. However, we do wish to retain copyright on the HOWTO documents, and would like to be notified of any plans to redistribute the HOWTOs.
If you have any questions, please contact <linux-howto@metalab.unc.edu>
No liability for the contents of this documents can be accepted. Use the concepts, examples and other content at your own risk. As this is a new edition of this document, there may be errors and inaccuracies, that may of course be damaging to your system. Proceed with caution, the author does not take any responsibility.
Who am I kidding? This is dangerous stuff! Stop reading immediately or risk lethal pollution of your systems!
All copyrights are held by their by their respective owners, unless specifically noted otherwise. Use of a term in this document should not be regarded as affecting the validity of any trademark or service mark.
Naming of particular products or brands should not be seen as endorsements.
You are strongly recommended to take a backup of your system before major installation and backups at regular intervals.
2002-03-09. Unfinished excerpt sent to Linux Documentation Project.
2002-03-11. Unfinished excerpt sent to Linux Documentation Project.
Section One step closer to the edge rewritten & finished.
2002-03-14. Unfinished snapshot.
Added epigraphs to all sections, removed one offending paragraph on the way.
Added example for large scale scanning in The plan.
Started section The entry point.
Started Credits.
2002-03-15. Unfinished snapshot.
First working example in The entry point.
Lots of small fixes about everywhere.
Renamed from "The Linux Virus Writing HOWTO".
Everything in this document is either plain obvious or has been written by someone else long time ago. My meager contribution is nice formatting, reproducibility and the idea to take the subject to mainstream media. But I'm certainly not innovative.
Silvio Cesare. <silvio@big.net.au> Founder of the trade. Keeper of the source. Check out http://www.big.net.au/~silvio and admire the release date.
John Reiser. <jreiser@BitWagon.com> Found one bug and two superfluous bytes in In the language of evil. Proved that I can't code a straight 23 byte "Hello World".
Feedback is most certainly welcome for this document. Please send your additions, comments and criticisms to the following email address: <alexander.bartolich@gmx.at>
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