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-
- =========================================================================
- ==Phrack Inc.==
-
- Volume One, Issue Six, Phile 5 of 13
-
- ===============================================================================
- ------------
- Unix Nasties
- ------------
- By Shooting Shark
-
- Written on April 3, 1986
- ===============================================================================
-
- Summary: Methods of sabotaging your favorite Unix system.
-
- Preface: I do not advocate utilizing ANY of the methods I put forth in this
- file. Unix is a cool operating system, perhaps one of the best
- systems ever designed in many respects. If you have access to a Unix
- system, you should LEARN UNIX AND LEARN C, because that is where the
- money is in the computer world. However, Unix is a relatively
- insecure operating system which is easy to fuck up. This file
- explains a few ways of doing so.
-
- Crash The System
- ----------------
- Unix has no built-in provision for the maximum amount of disk space allowed per
- user. Thus, one user can grab all the disk space on the system and effectively
- prevent anyone else from writing to the disk. A simple way of grabbing all the
- disk space is to create subdirectory after subdirectory until it is no longer
- possible. Here are a few ways of doing it.
-
- 1> Create a file with the following lines:
-
- mkdir subdir
- cd subdir
- source /u1/mydir/crash
-
- Call it crash. The last line ("source /u1/mydir/crash") should be altered
- so that it will look for the file in your directory. If your directory is
- /u3/students/jeff, the last line should say "source
- /u3/students/jeff/crash". After you write the above file, type:
-
- % source crash
-
- and wait...within a few minutes the program will abort because it won't
- have any more room on the disk. Neither will anyone else.
-
- 2> Here's a more elegant way of doing the same thing. Create this "endless
- loop" shellscript:
-
- while : ; do
- mkdir subdir
- cd subdir
- done
-
- and then "source" the file. If you are in the "sh" shell (if you are, you
- will probably have a "$" prompt) you can type "while : ; do" from the $
- prompt. You will then get a > prompt. Type the next three lines and sit
- back.
-
- 3> If you'd like to set the process in motion and hang up, and the file is
- called crash, type:
-
- % nohup source crash &
-
- and log off. This will start it as a background process, allowing you to
- log off. However, log off QUICKLY, since if you used the first example for
- your crash file, it will also eat up background processes like crazy which
- will also fuck up the system to some extent. Which brings us to...
-
- Slow Down The System Immensely
- ------------------------------
- There are many ways of doing this, the method being creating a sufficiently
- large number of background processes. Here's one specific example. Create a
- file called "slow1" with the following lines:
-
- w &
- source slow1
-
- create a file called "slow2" with:
-
- source slow1 &
- source slow2
-
- and execute slow2 with
-
- % slow2
- or
- % slow2 &
-
- This will create 25 background processes, each one running 25 background
- processes. The system will hardly move after you've got each one running.
-
- Messing Up A Directory
- ----------------------
- Many file-handling commands use "-" options. Create a file with a "-" at the
- beginning of its name by doing this:
-
- cat > -filename
-
- [now type a few lines, maybe something rude like "ha ha you can't delete this
- file".] Type a ^D (control-d) to end input. You now have a file called
- -filename in your directory. It will be VERY difficult to remove this file.
- If you were to try rm (remove) -filename or mv (rename) -filename, the rm or mv
- program would interpret -filename as an option, not a file, and would give you
- an error message telling you that -filename was not a valid option...thus, the
- file stays there obnoxiously.
-
- Create a couple of hundred files with "-" as the first characters in their
- names...it will be a royal pain for the person who is blessed with these new
- files, and they will probably just have to get a new login.
-
- Conclusion
-
- The use of any of these techniques is quite irresponsible, and if anyone did
- this to my Unix system, I'd be quite pissed. That is why I strongly recommend
- that you never use these tricks.
-
- So Long,
- Shooting Shark
-
- "Some people have a bad attitude, and I say, if they want to act tough, beat
- 'em up!" - Blue Oyster Cult
- -------------------------------------------------------------------------------
- For more information on UNIX sabotage and cracking, see the following articles:
-
- Ritchie, Dennis M. [he wrote Unix] "On the Security of UNIX." Programmers
- Manual for UNIX System III Volume II. Supplementary Documents.
-
- Filipski, Alan and Hanko, James. "Making UNIX Secure." BYTE Magazine, April
- 1986, pp 113-128.
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-