A Basic UNIX Overview.rtf

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\viewkind4\uc1\pard\tx0\tx959\tx1918\tx2877\tx3836\tx4795\tx5754\tx6713\tx7672\tx8631\f0\fs20 A Basic UNIX Overview\par
\par
Asriel\par
\par
\par
  UNIX FOR DOS ADDICTED WaReZ PuPPieZ AND THEIR PETS\par
\par
\par
  Introduction\par
  ------------\par
\par
  One of the most common operating systems in existance is Unix. Unix\par
  exists in many different flavors, from Berkeley BSD to AT&T System V\par
  to SunOs. Basic working knowledge of Unix is almost essential to a\par
  hacker, as it is the system a hacker is most likely to come across.\par
  If you intend to use the internet at all, or to do any serious\par
  exploration of Telenet, the ability to navigate through Unix is a\par
  necessity. (Unix is also the single most interesting system in\par
  existance: it's just fun to fuck with).\par
  \par
  Unix Logins\par
  -----------\par
\par
  Most Unix logins look essentially the same. A general Unix login\par
  prompt looks something like this:\par
\par
  connected to five.finger.com\par
  login:\par
\par
  That first line is the system identifier. Although it's not at all\par
  essential to what you are doing, it's good to know what system you are\par
  attempting to log on to.\par
  The second line is what typically identifies the system you are on as\par
  Unix. Almost all Unix systems greet a user with the same prompt:\par
  login:.\par
  Well, there's not much to do in Unix from the outside, and Unix\par
  systems are typically fairly secure at this point. You may be able to\par
  obtain a list of users, or current users, by logging in as 'who', but\par
  other than that there are few functions available here.\par
  Unless you are on the internet, or have accounts specifically for the\par
  specific machine you are on, the only way on to the system is to try\par
  the default passwords. What are the default passwords?\par
  Unix systems come installed with certain passwords automatically. In\par
  addition, some accounts must exist on a system. One such account is\par
  'root'. This user is the divine Kami of the Unix system... in short,\par
  an all access pass. Unfortunately, few systems allow root logins\par
  remotely, and even fewer leave 'root' unpassworded. Nevertheless, it's\par
  always worth a shot... try this:\par
\par
  connected to ren.stimpy.net\par
  login: root\par
  password: root\par
  invalid login\par
  login:\par
\par
  well, nice try anyways... other possible passwords for root include\par
  'sysadmin', 'sys', 'admin'... you get the idea. You may also want to\par
  try these passwords with a single digit appended (added, idiot) to\par
  them... meaning the password 'root' could be 'root1' or 'root2'.\par
  An interesting tip about passwords in general... many people that use\par
  passwords under 8 characters tend to add a digit or a non-alphanumeric\par
  character to the password. This is done in order to hinder guessing,\par
  and to stop password breakers (more on this later). In this case, you\par
  may want to try adding a space before root... or even an ascii 255 to\par
  the end.\par
  Fortunately, there is more than one default password in a unix\par
  system... a quick list:\par
\par
  sys        sys\par
  bin        bin\par
  daemon     daemon\par
  rje        rje\par
  setup      setup\par
  uucp       uucp/nuucp/anonymous\par
  nuucp      uucp/nuucp/anonymous\par
  mountfsys  mountfsys\par
\par
  In the System\par
  -------------\par
\par
  Ok, at this point, I'm going to assume you've gotten past the login...\par
  as painful as that may sound. Although Unix may be secure from the\par
  outside, without effort from the system administrators, the inside of\par
  the system is not.\par
  First off, you'll likely by asked for a terminal. vt100 serves your\par
  purposes sufficently, and it's typically the default, so hit enter.\par
  Now, hopefully, you have a prompt. There are many different types of\par
  unix prompts, some of which contain current directory information,\par
  some of which are just a single character. Just don't panic when my\par
  examples don't look exactly like what you've got on your screen.\par
  The first thing you *need* to do on the system is establish your tty\par
  paramters. As eldritch and arcane sounding as this term may seem, it's\par
  actually quite simple... you need to tell the system what keys are\par
  going to do what.\par
  The command to set these parameters is 'stty'. Watch:\par
\par
  squinkyB ] stty erase ^h\par
  squinkyB ]\par
\par
  There... that wasn't so bad, was it? Well, it's also pretty\par
  meaningless to you, unless you have the ascii table memorized and are\par
  pretty good at on-the-spot deduction.\par
  The tty erase parameters determines which key is to be used as a\par
  backspace. At times, this may already be set when you log in, or it\par
  may be set to a suitable alternate (such as delete). Most of the time\par
  the system will tell you when you log on if this is so. In this case,\par
  we've entered ^h in order to make the backspace key, appropriately\par
  enough, backspace.\par
  Another extremely important parameter is 'intr'. The 'intr' paramter\par
  tells the Unix system what you intend to use as a break character...\par
  you should have this set to ^c.\par
\par
  Getting Around\par
  --------------\par
\par
  A good thing to remember about Unix is that it's alot like DOS. Files\par
  are laid out in directories just as in DOS... in fact, the only\par
  immediate difference in the directory structures is that Unix uses a\par
  forward slash ("/", moron!) instead of a backwards one.\par
  Also, the basic Unix directory navigation command is identical to DOS.\par
  In order to change directories, you use the command 'chdir', or 'cd'.\par
  A quick example:\par
\par
  1 /usr1/astoria ] cd ..\par
  2 /usr ]\par
\par
  Wala. That simple. Quick notes:\par
\par
  \u1102? cd / will take you to root.\par
  \u1102? cd /*pathname* will take you to *pathname*\par
  \u1102? cd home will take you to your home directory.\par
\par
  You can make and delete your own directories with the mkdir/rmdir\par
  commands. Simply put, mkdir makes a subdirectory off of the current\par
  directory, and rmdir removes a subdirectory from the current\par
  subdirectory. Good to know if you plan to do a lot of file transfers.\par
  An important note about Unix directories, files, and concepts:\par
  Unix is a case-sensitive operating system. Thus, the files\par
\par
  \u1102? Spleen\par
  \u1102? spleen\par
  \u1102? SPLEEN\par
  \u1102? SpLeEn\par
\par
  are all different. This rule applies to directories and command line\par
  paramters, as well as most other Unix ideas.\par
  Another nice thing to know about Unix: Unix files are not subject to\par
  the normal DOS 8 character limit. Thus, you can have vast filenames,\par
  such as "this_file_ate_my_biscuit".\par
\par
  Some other important commands\par
  -----------------------------\par
\par
  First and foremost, you should know cp. cp is the basic Unix\par
  equivalent of the DOS COPY command. The command line for cp is\par
  identical to that of COPY.\par
  Next on the scale of cosmic import is cat. cat is the Unix equivalent\par
  of the DOS TYPE command, and once again, for simple file displaying,\par
  the command line is identical.\par
   Variations on the theme:\par
   pg: displayes a file page by page. Type "pg x filename", where x is a\par
       number of lines to display before pausing and filename is the\par
       file you wish to display.\par
   more: displays a file screen by screen.\par
   Stupid pet trick:\par
   You can use your cat to copy files, simply by using the directional\par
   operators. To copy a file from here to there using cat, simply type:\par
\par
   % cat here\par
   this is the file here\par
   % cat there\par
   this is the file there\par
   % cat here > there\par
   % cat there\par
   this is the file here\par
\par
   The operator ">" simply takes the output from the cat command and\par
   places is in the location specified after it.\par
  Another vital command to know is 'rm'. rm deletes a file from the\par
  system, in the same way DEL would on a DOS system. Not to much else to\par
  say.\par
  Critical in your navigation of a Unix system is the ls command. ls is\par
  DOS DIR on heroin. Simply type ls and you get a nice, neat list of\par
  files in the directory.\par
   DIR on controlled substances:\par
   There are a few command line parameters that you should know...\par
   foremost is l. ls -l gets you a list of files, and valuable\par
   information about each file, including permissions (more on that\par
   later), size, and linked files.\par
   Another useful command for long file lists is C. ls -C gets you a\par
   list of files in multiple columns, much the same as DIR /W would\par
   merit a double column report of all existing files. A quick reminder:\par
   ls -C is NOT the same as ls -c. Unix = case sensitive.\par
  Another good command to know, mv will move a file from directory to\par
  directory. For those of you without DOS 6.0 <gasp>, mv simply copies a\par
  file to another directory and deletes the original.\par
   quick tip for files on the lam:\par
   if you want to rename a file (to protect the innocent), you need to\par
   mv a file to a different file name. A quick demo:\par
\par
   # ls\par
   myfile\par
   # cat myfile\par
   this is my file\par
   # mv myfile my_other_file\par
   # ls\par
   my_other_file\par
   # cat my_other_file\par
   this is my file\par
\par
  Another vastly important command is 'man'. In fact, man is probably\par
  one of the most important commands extant for a beginning user... it\par
  calls up the system's help files. To use man, simply type in 'man\par
  command', where command is a Unix command you seek to gain\par
  enlightenment regarding. It's a great way to gain an understanding of\par
  Unix commandline parameters.\par
  If you are interested in seeing who's been on of late, or just want a\par
  few names to try to hack, type 'who'. You get a quick list of users\par
  that have accessed the system lately. If you <god forbid> need to know\par
  who you are at this point, type 'whoami'.\par
  If you want to change your identity on the system, type 'su name'\par
  where name is an account on the system. It'll ask you for the account\par
  password, then, *presto*... instant transmogrification.\par
   A Caveat for smart alec hackers:\par
   Unix typically logs usage of the su command. While su may seem like a\par
   great opportunity to try to hack out passwords manually without\par
   worrying about the system hanging up after 3 attempts, it's typically\par
   not a good idea to do this, as it may alert the administrators to\par
   your presence.\par
  *Numero Uno on the list of commands NEVER to use on a Unix system:\par
  The 'passwd' command changes your password on a Unix system. Seems\par
  innocous enough, eh? Uh-uh. If your account is active, and there's a\par
  very strong chance that it either is or will be, there is no better\par
  way to lose the account than to change the password, only to have the\par
  legitimate user alert the sysadmins when he/she can't gain access to\par
  his/her normal account (well, there are better ways... you could\par
  simply mail the sysadmin and tell him you are trying to hack his\par
  grandmother's life support machine through your account).\par
  I've seen this single, quick command turn a extremely lax system\par
  into an ironclad security compound in less than a day.\par
  DONT-FUCK-WITH-IT.\par
  *Numero Dos on that same list:\par
  The 'mail' command reads and sends mail. So what? Well, unless your\par
  account is stable (and it isn't unless you either paid for it or\par
  killed the original owner in such a way that his body cannot claw it's\par
  way out of it's grave to it's keyboard), the user is more likely than\par
  not going to know if you read his mail. In addition, if you send mail\par
  out of the system (type 'mail', and a username/address; type in your\par
  message and end it with a ^d on it's own line), the response from your\par
  message will likewise alert the user to your presence.\par
\par
  System Spelunking\par
  -----------------\par
\par
  The first place you want to check out in the wild uncharted directory\par
  tree of your friendly neighborhood Unix system is the "/etc"\par
  directory. What's in it? The single most intensely important file on\par
  the system (besides a world writable root owned SUID file... but don't\par
  worry about that)... the passwd file.\par
  What is in the passwd file?\par
\par
  \u1102?  a list of all accounts on the system\par
  \u1102?  a list of the passwords for these accounts\par
  \u1102?  a list of access levels for these accounts\par
  \u1102?  a list of the home directories for these accounts\par
  \u1102?  a list of information pertaining to these accounts.\par
\par
  Why the hell the Unix designers decided this file should be world\par
  readable is beyond me. Be content to know that your standard everyday\par
  run-of-the-mill-lacking-in-certified-cosmic-power 'cat' command WILL\par
  display this file. As will pg and more. However, because most users\par
  don't have write permissions (more on that later) to the /etc\par
  directory, 'cat' is pretty much the only applicable command here.\par
  However, if you need to copy the file to your own directory (for\par
  whatever reason), just cat it there with the directional operator (>).\par
  The catch:\par
  Well, there are two catches here. First off, regardless of system\par
  security, if the passwords are in the file, they are encrypted. You\par
  can't decrypt them. Although you can get a list of accounts without\par
  passwords this way (just look for accounts with no entry in the\par
  password field), and a list of accounts that can't be logged onto\par
  remotely/at all (NO LOGIN), you can't get much else. Sucks, don't it?\par
  Notice I said 'if' the passwords are there.\par
  <ominous soundtrack please>\par
  Some horrible, paranoid, draconian system administrators mutilate\par
  their passwd files in such a way that (*gasp*) the passwords don't\par
  show up. All you get is one cold, icy X staring at you from the bowels\par
  of Unix Shell Siberia, mocking you as you pull your hair out in\par
  frustration (sorry, but this is a sore spot with me). The kidnapped\par
  passwords reside in the shadow file in the /etc directory, available\par
  with your standard everyday run-of-the-mill-but-distinct-in-the-fact-\par
  that-only-root-level-accounts-can-use-it-to-this-extent 'cat' command.\par
  Well, if the passwords are encrypted, what good are they?\par
  By themselves, nothing. A account with a Unix encrypted password will\par
  get you no further than an account with no listed password at all. You\par
  can't even deduce the amount of characters in the password if it's\par
  encrypted. So what's the use?\par
  The Unix method of encrypting files is available to the public. It is\par
  also, to most mortals, irreversable. Essentially, this means you can\par
  encrypt a string of characters, but not decrypt it. Even the unix\par
  system itself doesn't decrypt the password when you log on...\par
  When you log on, the Unix system takes whatever you enter at the\par
  password prompt, encrypts it, and matches it to the entry in the\par
  passwd file. Thus, the Unix system never decrypts the password... it\par
  only compares it to a different encrypted string.\par
  While this may not sound too particularly useful at first, it is.\par
  There are programs that have been written to do the same thing on a\par
  personal computer... you supply it a list of passwords and a list of\par
  words to attempt to use as passwords (called dictionaries), and it\par
  spends the night encrypting dictionaries and matching them to password\par
  entries. By running a dictionary through a passwd file, on a typical\par
  system, you can usually get 10-20 accounts. Good personal computer\par
  examples of this program idea include Killer Cracker (the industry\par
  standard, so to speak) and CrackerJack (faster than Killer Cracker).\par
   Quick tips for CrackerJunkies with leech access at an H/P BBS:\par
   A standard dictionary will not uncover passwords protected with an\par
   appended digit or non-alphanumeric character. In order to get around\par
   this, you need only grab a program that processes the dictionary file\par
   to add that digit to each entry in the dictionary... although this\par
   takes longer, and you'll need to do it multiple times, you can\par
   typically get 10 more accounts just by adding a 1 to every entry.\par
  Files and directories in Unix are characterized further by their\par
  permissions. Permissions are a standard system of who gets access to a\par
  specific function of that file or directory. Standard permissions\par
  include read, write, and execute. You can get a list of permissions by\par
  typing 'ls -l'. The first field in the listing contains the\par
  permissions, grouped as follows:\par
\par
  owner  group   world\par
  --------------------\par
  rwx    rwx     rwx\par
\par
  (Not drawn to scale... in fact, it doesn't look anything like that).\par
  Essentially, as long as the letter is there, you have access to that\par
  facet of the file. If the letter is not there, you'll see a dash...\par
  meaning you don't have access to that function. An example:\par
\par
  rwxr-x--x\par
\par
  In this case, the owner of the file can Read the file, Write to the\par
  file, and eXecute the file; members of his group (a bunch of linked\par
  accounts) can Read the file, CANNOT Write to the file, and can eXecute\par
  the file; and the rest of the user population CANNOT Read or Write to\par
  the file, but CAN eXecute the file.\par
\par
  rwx---rwx\par
\par
  is a WORLD-READABLE, WORLD-WRITABLE, WORLD-EXECUTABLE file. This\par
  simply means that anyone can read, write, or execute the file.\par
\par
  Another permission sometimes set to a file is the SUID bit. An SUID\par
  file contains a smallcase s in the user executable section of the\par
  permissions list...\par
\par
  rws--x--x\par
\par
  When you execute an SUID file, your user ID becomes that of the owner\par
  of the file. While this may not look to important at first, by now you\par
  should know that no really important super elite hacker concept does.\par
  Take a look at this:\par
\par
  rwsr-x--x\par
\par
  Synopsis? It's a world executable SUID file. In essence, anyone can\par
  execute the file, and in doing so, become the owner of the file for\par
  the duration of the time that file is operating. However, this doesn't\par
  get you much, because you typically can't do anything while the\par
  programis running. More likely than not, it's calculating how many\par
  pencils it needs to order for school tomorrow or some other such\par
  drivel.\par
  The real power of the SUID file comes into play in this situation:\par
\par
  rwsrwxrwx\par
\par
  You won't see a lot of these, but when you do, look out. What you have\par
  here is a world writable SUID file... and a world writable program can\par
  be any program on the system you have read access to. Like, say,\par
  /bin/sh... the Unix shell...\par
  Quick command line example... 'diablo' is a root owned, world writable\par
  SUID file. I'm going to ignore the rest of the output of the ls\par
  command.\par
\par
  #ls -l\par
  rwsrwxrwx... ...diablo\par
  #cat /bin/sh > diablo\par
  #diablo\par
  $\par
\par
  Oh, just so you know, the $ prompt denotes root access.\par
  Good deal, huh? In general, if you have right privs to an SUID file,\par
  copy it to your own directory and cat /bin/sh into it. You now have an\par
  instant gateway to the account of the owner of that file.\par
  If you want to find files that you can do this with, try this out:\par
\par
  #find / -user root -perm -4000 -exec /bin/ls -al \{\} ";"\par
\par
  This will give you a list of all root owned SUID files. If you want\par
  more info on the 'find' command, just 'man find'.\par
\par
  Well, I'm overdo for an appointment on the IRC in #warez... so I'll\par
  cut off here. I hope I've been of assistance to you.\par
\par
----------------------------------------------------------------------------\par
  A C T U A L  A R T I C L E  E N D S  H E R E . . .\par
\par
  Please feel free to save an extra 1k of file space and invoke the DOS\par
  EDIT CUT command at the dotted line. Do not remove the rest of this\par
  article on penalty of law.\par
\par
  S00P3R GR00P-3SQU3 GR33TZ / +HANX\par
\par
  Greets go out to Nowhere Man, INC, THG, UNT, SaD, SoD, PTA, SOB\par
  Thanks to... ________________________\par
                     your ad here\par
\par
  Current DWE Akshul M3mbre Boards:\par
\par
  Nitro Burnin' Funny Cars    WHQ/DWEnet HOST     (312)582-1115  <XANAX>\par
  The Prodigal Sun            CHQ/MECCA           (312)238-3585  <ASRIEL>\par
  Dark Waters                 HQ/Infosite         (312)667-0222  <MONK>\par
  PyroTechnics II             Infosite            (708)991-9403  <PYRO>\par
\par
  DWE M3/\\/\\B3R LiST\par
\par
  President and Dictator for Life: Xanax\par
  Head Courier/Warez Cracker: Asriel\par
  Head Fisherman/Trout Expert: Changeling\par
  Head Person That Gets Asriel Free CDs: Monk\par
  Head Person That Gets DWE Members Free WaReZ: Pyro\par
  Head Person That Knows More Than Asriel (Honorary Title): LVX\par
  Head Person That Actually Wrote for DWE without Coercion: Cosmos\par
  Head Know-It-All Stoner that runs 386bsd: Goldstein\par
\par
  Want to write for DWE? Neither do we. But if the spirit moves you,\par
  write up an article about anything we haven't discussed already, and\par
  post it somewhere in DWEnet or at any of the member boards, or call\par
  any of the members voice and dictate it to them, or submit it to them\par
  school newspaper of any of the members, or tack it on a bulletin board\par
  in the Third Coast Cafe in Century Mall, and chances are it'll be\par
  released as a s00per c00l DWE article.\par
\par
 W H A T  F O L L O W S  M U S T  N O T  B E  D E L E T E D\par
---------------------------------------------------------------------------\par
  (c) 2003 Hackers-Network\par
  Asriel(tm) appears courtesy of Hasbro, Inc.\par
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