UNIX Use and Security - By the Prophet, Komputer, More Hacking

[ Pobierz całość w formacie PDF ]
1)U **************************************************************************************************** **** Unix Use and Security From **** The Ground Up **** **** by **** **** The Prophet **** **** ****************************************************************************************************December 5, 1986.INTRODUCTION------------The Unix operating system is one of the most heavily used mainframeoperating systems today. It runs on many different computers (Dec VAX's, AT&T's3bx series, PDP-11's, and just about any other you can think of- includingPC's), and there are many different, but pretty much similar, versions of it.These Unix clones go by many different names- here are the most common: Xenix,Ultrix, Ros, IX/370 (for the IBM 370), PCIX (for the IBM PC), and Berkely (BSD)Unix. This file will concentrate on AT&T System V Unix, probably the mostheavily used version. (The next most heavily used is Berkely Unix.) This filewill cover just about everything all but THE most advanced hacker will need toknow about the Unix system, from the most rodent information to advancedhacking techniques. This is the second version of this file, and as I discoverany errors or new tricks, I will update it. This file is, to the best of myknowledge, totally accurate, however, and the techniques in it will work justas described herein. Note, that these techniques will work on System V Unix.Not necessarily all, but most, should work on most other versions of Unix aswell. Later, if this file is received well, and there is demand for another, Iwill release a file on yet more advanced techniques. If you wish to contact me,I can be reached several ways. First, on these boards:Shadow Spawn 219-659-1503Private Sector 201-366-4431 (As prophet, not The Prophet...some rodent stolemy name.)Ripco 312-528-5020Stalag 13 215-657-8523Phreak Klass 2600 806-799-0016Or at this voice message system:800-556-7001Box 7023I welcome any suggestions, corrections, or feedback of any kind. And lastly,thanks for taking the time to read this:THE USUAL DISCLAIMER:---------------------This file is for [of course] informational purposes only. <Snicker> Idon't take responsibility for anything anyone does after reading this file._______________________________________________________________________________IDENTIFYING UNIX SYSTEMS AND LOGGING IN---------------------------------------A Unix system can easily be identified by its prompts. When you firstconnect to a Unix system, you should receive the login prompt, which is usually"Login:" (Note, that the first character may or may not be capitalized.) Onsome systems, this prompt may be ";Login:" or "User:" (Again, the first lettermay or may not be capitalized.) This may be preceded by a short message,(usually something like "WARNING!!! This system is for authorized usersonly!"), the name of the company that owns the system, or the uucp network nameof the system. (The uucp facilities will be explained in detail later.) At thispoint, you should enter the user name and press return. (You should be inlowercase if your terminal supports it.) You should then receive the passwordprompt, "Password:" (And yet again, the "P" may or may not be capitalized.) Atthis point, you should enter your password and press return. If you havespecified the correct username/password pair, you will then be admitted intothe system. If you have entered a non-existant username or an incorrectpassword, you will receive the message "Login incorrect" and will be returnedto the login prompt. There is little information given before login, and thereis no way to find valid usernames from pre-login information.There are no "default" passwords in Unix. When the system is initiallyset up, none of the default accounts or any of the accounts created by thesystem operators has a password, until the system operator or the account ownerset one for the account. Often, lazy system operators and unwary users do notbother to password many (and in some cases, all) of these accounts. To log inunder an account that doesn't have a password, you have only to enter theusername at the login prompt.You may encounter some occasional error messages when attempting to login under certain accounts. Here are some of the more common messages, and theircauses:1. "Unable to change directory to /usr/whatever"-This means that theaccount's home directory, the directory which it is placed inupon logon, does not exist. On some systems, this may preventyou from logging under that account, and you will be returnedto the login prompt. On other systems, you will simply beplaced in the root directory. If this is the case, you willsee the message "Changing directory to '/'".2. "No shell"-this means that the account's shell, or commandinterpreter does not exist. On some systems, the account willnot be allowed to log in, and you will be returned to the loginprompt. On other systems, the account will be admitted into thesystem using a default shell, usually the Bourne shell. (Theshell will be explained later.) If this is the case, you willsee the message "Using /bin/sh".UNIX ACCOUNTS-------------There are two types of Unix accounts-user and superuser accounts. Useraccounts are the normal user accounts. These accounts have no privileges.Superuser accounts are the system operator accounts. These accounts have fullprivileges, and are not bound by the file and directory protections of otherusers. In Unix, there is no hierarchy of privileges-either an account has fullprivileges, or it has none.Unix usernames are up to 14 characters long, but usually are within therange of 1-8. The usernames can contain almost any characters, includingcontrol and special characters. (The accounts will usually not contain thecharacters @, control-d, control-j, or control-x, as these characters havespecial meanings to the Unix operating system.) The Unix system comes initiallyconfigured with quite a few default accounts, some of which are superuser andsome of which are only user-level accounts. Here is a list of the defaultaccounts which usually have superuser privileges:root (Always!)makefsysmountfsysumountfsyscheckfsysThe root account is always present on the system, and always has superusercapabilities. (Note: most Unix System V systems come initially set up with asecurity feature that prevents superuser accounts from logging in remotely. Ifyou attempt to log in under a superuser account remotely on a system with thisfeature, you will receive the message "Not on console", and will be refusedadmission to the operating system. This will NOT prevent you from usingsuperuser accounts remotely-you simply have to log in under a user account andthen switch over to a superuser account using the su utility, which will bedescribed later.)Here is a list of the user-level default accounts:lpdaemontroublenuucpuucpbinrjeadmsysadmsyncThe bin account, although it is only a user account, is particularly powerful,as it has ownership of many of the system's important directories and files.Although these are the only default accounts on System V Unix, there are manyother accounts which I have found to be common to many Unix systems. Here is alist of some of the accounts I have found on many Unix systems:batch admin user demo testfield unix guest pub publicstandard games general student helpgsa tty lpadminAlso try variations on the account names, such as rje1, rje2, user1, user2,etc. Also, try variations on people's names and initials, such as doej, doe,john, johnd, jjd, etc.No matter what the format for the usernames, one thing is common to allsystems-almost all of the usernames will begin with a lowercase letter. Thereis a good reason for this-when logging into the system, if the first characterof the username you type in is in uppr-case, the system automatically assumesthat your terminal does not support lower-case. It will then send all output toyou in upper-case, with characters that are supposed to be upper-case precededby a backslash ("\", the Unix escape character), to differentiate them from thecharacters which are meant to be in lower-case. Unix *always* differentiatesbetween the cases, so it is best to stay in lower-case while on the system.As mentioned before, there are no "default" passwords on Unix. When anaccount is created, it has no password, until the superuser or the account'sowner sets one for it. Unix passwords are a maximum of 11 characters. Thepassword may contain any character, and the system distinguishes between upperand lower case characters. Many Unix systems implement a special securityfeature und... [ Pobierz całość w formacie PDF ]

  • zanotowane.pl
  • doc.pisz.pl
  • pdf.pisz.pl
  • emaginacja.xlx.pl

    •