*** A List Of Some OF The Most Useful UNIX **     *** Hacking Commands, and Some Hints On Their Usage ***       ---------------------------------------------------------------     It is fun and often usefull to create a file that is owned by someone else.  On most systems with slack security ie 99% of all UNIX systems, this is quite easily done.  The chown command will change any of your files to make someone else the owner. Format is as follows:chown ownername filelist Where ownername is the new owner, and filelist is the list of files to change.  You must own the file which your are goin to change, unless you are a superuser....then u can change ANYTHING!     chgrp is a similar command which will change the group ownership on a file.  If you are going to do both a chown and a chgrp on a file, then make sure you do the chgrp first!  Once the file is owned by someone else, you cant change nything about it!---------------------------------------------------------------     Sometimes just seeing who is on the system is a challenge in itself.  The best way is to write your own version of who in C, but if you can't do that then this may be of some help to you:     who   followed by on or more of the following flags:          -b Displays time sys as last booted.          -H Precedes output with header.          -l Lists lines waiting for users to logon.          -q displays number of users logged on.          -t displays time sys clock was last changed.          -T displays the state field (a + indicates it is possible to send to terminal, a - means u cannot)          -u Give a complete listing of those logged on.   **who -HTu is about the best choice for the average user**##by the way, the list of users logged on is kept in the file /etc/utmp.  If you want to write your own personalised version of who in C, you now know where to look!###---------------------------------------------------------------      When a users state field (see -T flag option for who command) says that a user has their message function on, this actually means that it is possible to get stuff onto their screen.     Basically, every terminal on the system has a file corresponding to it.  These files can be found in the /dev directory.  You can to anything to these files, so long as you have access -eg you can read them, and write to them, but you will notice that they never change in size.  They are called character specific files, and are really the link between the system and the terminals.  Whatever you put in these files will go staright to the terminal it corresponds to.     Unfortunately, on most systems, when the user logs in, the "mesg n" command is issued which turns off write access to that terminal, BUT- if you can start cating to that terminal before system issues the mesg n command, then you will continue to be able to get stuff up on that terminal! This has many varied uses.     Check out the terminal, or terminal software being used.  Often you will be able to remotely program another users terminal, simply by 'cating' a string to a users screen.  You might be able to set up a buffer, capturing all that is typed, or you may be able to send the terminal into a frenzy- (sometimes a user will walk away without realizing that they are sill effectively logged on, leaving you with access to their account!).  Some terminal types also have this great command called transmit screen. It transmits everything on the screen, just as if the user had typed it !     So just say I wanted to log off a user, then I would send a clear screen command (usually ctrl l), followed by "exit" followed by a carriage return, followed by the transmit screen code.  Using ths technique you can wipe peoples directories or anything.  My favourite is to set open access on all their files and directories so I can peruse them for deletion etc at my own leisure).            ---------------------------------------------------------------     If you ever briefly get access to another persons account eg. they leave the room to go to toilet or whatever, then simply type the following:chmod 777 $HOMEchmod 777 $MAIL     Then clear the screen so they dont see what you just typed.     Now you can go look at their directory, and their mail, and you can even put mail in their mail file. (just use the same format as any mail that is already there!). Next time they log in the system will automatically inform them they have new mail!---------------------------------------------------------------     Another way to send fake mail to people is to use the mail server.  This method produces mail that is slightly different to normal, so anyone who uses UNIX a bit may be suspiscious when they receive it, but it will fool the average  user!type telnetthe following prompt will appear:telnet>now type :open localhost 25some crap will come up about the mail server..now type:mail from: xxxxxx     Put any name you want.some more bullshit will come up. Now type:rcpt to: xxxxxx  Put the name of the person to receive mail here.now type:datanow you can type the letter...end it with a "."type quit to exit once you are done.-------------------------------------------------------------     Heres one for any experimenters out there...It is possible to create files which simply cannot be deleted from the standard shell.  To do this you will have to physically CREATE THE FILE USING A C PROGRAM or SCRIPT FILE, and you will have to use a sequence of control characters which cannot be typed from the shell.  Try things like Ctrl-h (this is the code for the delete key).  Just a file with the name Ctrl-h would not be deleteable from the shell, unless you used wildcards. So, make it a nice long series of characters, so that to delete the file, the user has no choice but to individually copy all his files elsewhere, then delete everything in his directory, and then copy all his files back.....this is one of my favourites..gets em every time!          The following script file is an example which will create a file with the name Ctrl-h.  You MUST tyoe this file in using the vi editor or similar.*****If you are not very good with vi, type "man vi" and print the help file...it even contains stuff that I find useful now and then.*****type the following in vi...echo'' > 'a^h'  ***NOTE...to get the ^h (this really means ctrl-h) from vi type:Ctrl vCtrl h   The Ctrl v instrcts vi to take the next character as a ascii character, and not to interpret it.     change the access on the file you just created and now execute it.  It will create a file which looks like it is called a, but try to delete it !..use wildcards if you really want to delete it. *> Title:   Tutorial on hacking through a UNIX system**  In the following file, all references made to the name Unix, may also be substituted to the Xenix operating system.  Brief history:  Back in the early sixties, during the development of third generation computers at MIT, a group of programmers studying the potential of computers, discovered their ability of performing two or more tasks simultaneously.  Bell Labs, taking notice of this discovery, provided funds for their developmental scientists to investigate into this new frontier.  After about 2 years of developmental research, they produced an operating system they called "Unix".  Sixties to Current:  During this time Bell Systems installed the Unix system to provide their computer operators with the ability to multitask so that they could become more productive, and efficient.  One of the systems theyput on the Unix system was called "Elmos". Through Elmos many tasks (i.e.billing,and installation records) could be done by many people using the same mainframe.  Note: Cosmos is accessed through the Elmos system.  Current:  Today, with the development of micro computers, such multitasking can be achieved by a scaled down version of Unix (but just as powerful).  Microsoft,seeing this development, opted to develop their own Unix like system for the IBM line of PC/XT's.  Their result they called Xenix (pronounced zee-nicks).  Both Unix and Xenix can be easily installed on IBM PC's and offer the same function (just 2 different vendors).  Note: Due to the many different versions of Unix (Berkley Unix, Bell System III, and System V the most popular) many commands following may/may not work. I have written them in System V routines. Unix/Xenix operating systems will be considered identical systems below.  How to tell if/if not you are on a Unix system:  Unix systems are quite common systems across the country. Their security appears as such:  Login;     (or login;) password:  When hacking on a Unix system it is best to use lowercase because the Unix system commands are all done in lower- case. Login; is a 1-8 character field. It is usually the name (i.e. joe or fred) of the user, or initials (i.e. j.jones or f.wilson).  Hints for login names can be found trashing the location of the dial-up (use your CN/A to find where the computer is). Password: is a 1-8 character password assigned by the sysop or chosen by the user.       Common default logins    --------------------------    login;       Password:    root         root,system,etc..    sys          sys,system    daemon       daemon    uucp         uucp    tty          tty    test         test    unix         unix    bin          bin    adm          adm    who          who    learn        learn    uuhost       uuhost    nuucp        nuucp  If you guess a login name and you are not asked for a password, and have accessed to the system, then you have what is known as a non-gifted account. If you guess a correct login and pass- word, then you have a user account. And, if you get the root p/w you have a "super-user" account. All Unix systems have the following installed to their system: root, sys, bin, daemon, uucp, adm Once you are in the system, you will get a prompt. Common prompts are:  $ % #  But can be just about anything the sysop or user wants it to be.  Things to do when you are in: Some of the commands that you may want to try follow below:  who is on  (shows who is currently logged on the system.) write name (name is the person you wish to chat with) To exit chat mode try ctrl-D. EOT=End of Transfer. ls -a      (list all files in current   directory.) du -a      (checks amount of memory  your files use;disk usage) cd\name    (name is the name of the sub-directory you choose) cd\        (brings your home directory  to current use) cat name   (name is a filename either  a program or documentation  your username has written)  Most Unix programs are written  in the C language or Pascal  since Unix is a programmers'  environment. One of the first things done on the system is print up or capture (in a buffer) the file containing all user names and accounts. This can be done by doing the following command:  cat /etc/passwd  If you are successful you will see a list of all accounts on the system.  It should look like this:  root:hvnsdcf:0:0:root dir:/: joe:majdnfd:1:1:Joe Cool:/bin:/bin/joe hal::1:2:Hal Smith:/bin:/bin/hal  The "root" line tells the following info : login name=root hvnsdcf   = encrypted password 0         = user group number 0         = user number root dir  = name of user /         = root directory  In the Joe login, the last part "/bin/joe " tells us which directory is his home directory (joe) is. In the "hal" example the login name is followed by 2 colons, that means that there is no password needed to get in using his name.  Conclusion:  I hope that this file will help other novice Unix hackers obtain access to the Unix/Xenix systems that they may find.                      On the Security of UNIX                      =-=-=-=-=-=-=-=-=-=-=-=Recently there has been much interest in the security aspects of operatingsystems and software.At issue is the ability to prevent undesired disclosure ofinformation, destruction of information,and harm to the functioning of thesystem.This paper discusses the degree of security which can be provided underthe system and offers a number of hints on how to improve security.The firstfact to face is that UNIX was not developed with security,in any realisticsense,in mind;this fact alone guarantees a vast number of holes.(Actually thesame statement can be made with respect to most systems.)The area of security in which is theoretically weakest is in protecting againstcrashing or at least crippling the operation of the system.The problem here isnot mainly in uncritical acceptance of bad parameters to system calls (theremay be bugs in this area, but none are known)but rather in lack of checks forexcessive consumption of resources.Most notably, there is no limit on the amount of disk storage used, either intotal space allocated or in the number of files or directories.Here is aparticularly ghastly shell sequence guaranteed to stop the system: