an indepth guide in hacking unix and the concept of basic net.txt

黑客培训教程

-rwxr-x--- is read in triples of 3.The first chracter eg(-,d,b,c)-means as
follows: - is an ordinary file ,d is a directory,b is block file,c is a
chracter file.
The r stands for read permission,w is write permission,x is execute.The first
colum is read in 3 triples as stated above.The first group of 3 (in -rwxr-x---)
after the "-" specifies the permission for the owner of the file,the second
triple are for the groups (the fourth colum) and the last triple are the      
permissions for all other users.Therefore the -rwxr-x--- is read as follows.
The owner john has permission to read,write and execute anything in the bin
directory but the group has no write permission to it and the rest of the users
have no permission at all.The format of one of the lines in the above output
is as follows:

file type-permissions,links,usersname,group,bytes taken,date,time when last
renued,directory or file name.
**You will be able to read,execute cathys file named party due to the same
group***

chmod                    
-----             
The chmod command changes permission of a directory or a file.Format is
chmod who+,-,=r,w,x
The who is substituted by u-user,g-group,o-other users,a-all.
The + means add permission,- means remove permission,= - assign.  
Example :If you wanted all other users to read the file name mail ,type:   

$ chmod o+r mail
 
cat         
---          
Now suppose you wanted to read the file letter .There are teo ways to doing
this.First go to the michelle directory then type in:

$ cat letter
line one ...\
line two ... }the output of letter
line three../
$
   or
If you are in the parent directory type in:
$ cat /usr/john/michelle/letter
and you will have the same output.

Some cat options are  -s,-u,-v,-e,-t

Special Chracters in Unix:
-------------------------
*  - matches any number of single characters eg. ls john* will list
     all files that begin with john
[...] - matchs any one of the chracter in the [ ]
? - matches any single chracter
runs a process in the backgroung leaving your terminal free
$ - Values used for variables also $n - null argument
> - redirectes output
< - redirects input to come from a file
>> - redirects command to be added to the end of a file
| - pipe output (eg:who|wc-l tells us how many users are online)
"..." - Turn of meaning of special chracters excluding $,`
`...` - allows command output in to be used in a command line
'...' - turns of special meaning of all chracters

continuation of local commands...[     ] -contains the options used
------------------------------- 
passwd
------
Password changing seems to be a big thing among the savants.Anyway to change
the password one would use the 'passwd' command as shown below:

   $passwd
   Changing password for john
   Old password:                              
   New password:                              
   Retype new password:
   $
  
This will only work when the password has aged enough

ps
--
Its sometimes necessary to see what command procesess you are running,this
command lets you see that.
ps [-a all processes except group leaders] [-e all processes] [-f the whole
   list]                                                           

   $ps
   PID   TTY  TIME   COMMAND
   200   tty09 14:20  ps

   The systems reports (PID - process idenetification number which is a #
   from 1-30,000 assigned to UNIX processes)
   It also reports the TTY,TIME and the COMMAND being executed at the time.
   To stop a process enter :    

   $kill [PID] (this case its 200)
   200 terminated
   $

grep
----
This comand is important when seaching for a word or words in large files.

grep [argument] [file name] - searchs for an file that contains the argument
                              for example:
   $ grep phone cathy
    phone   michelle  (718)5551234
    phone   cindy   (718)5553456

    What this did was to find the argument 'phone' in the file cathy.If the
    argument consists of two or more words then  it must be enclosed in single
    quotes.


mv
--
mv [file names(s)] [ dir name ] - renames a file or moves it to another     
                                  directory eg.      
   $mv letter letters 
   $
   This renames the file letter to letters thereby deleting letter
                  or if you want to move files then
   $mv /usr/john/pers/capital /usr/john/michelle/capital
   $   
   This moves the file capital to the directory named michelle

diff
----
diff [file name] [ file name] - show diffrence between two files.Output of this
                                will have something like 4,5c4,5 then the it
                                will display both sets of files on the screen
                                The 4,5c4,5 means that you must change "c"
                                lines 4 to 5 in one file to line 4 to 5 in   
                                another.
      Option for using this command are :
       -b  -  it ignores blank spaces
       -h  - compares it quickly
       -s  - reports files that are the same
       -S[file] - this is when you want to compare a directory starting at a
                  specific file
       

       There is also a command to compare 3 files which is :   
 
       diff3 [options] [file1] [file2] [file3]

cp
--
cp [file name] [file name] - makes a copy of a file

   $ cp letter letters
   $
   The file letters is a dupilcate copy of letter.In this case the original
   is not erased like in the mv command



.... more UNIX commands:
--------------------

man [command] or [c/r] -will give you a list of commands explainations

help - available on some UNIX systems
                  
mkdir [dir name(s)] - makes a directory      

rmdir [dir name(s)] - removes directory.You wont be able to remove the
                      directory if it contains files in them

rm [file name(s)] - removes files. rm * will erase all files in the current
                    dir.Be carefull you!!.Some options are :                
                    [-f unconditional removal] [-i Prompts user for y or n]
                        
write [login name ] - to write to other logged in users.Sort of a chat

mesg [-n] [-y] - doesn't allow others to send you messages using the write
                 command.Wall used by system adm overrides it.

$ [file name] - to execute any file

wc [file name] - Counts words,chracters,lines in a file

stty [modes] - Set terminal I/O for the current devices

sort [filename] - Sorts and merges files many options

spell [file name] > [file name] - The second file is where the misspelt words
                                  are entered

date [+%m%d%y*] [+%H%%M%S] - Displays date acoording to options

at [-r] [-l] [job] - Does a specified job at a specified time.The -r Removes 
                     all previously scheduled jobs.The -l reports the job #
                     and status of all jobs scheduled

write [login] [tty] - Sends message to the login name.Chat!



su [login name]
---------------
The su command allows one to switch user to a super user to a user.Very
important could be used to switch to super user accounts.
Usage:                                                

$ su sysadm
password:

This su command will be monitored in /usr/adm/sulog and this file of all files
is carefully monitered by the system administrator.Suppose you hacked in johns
account and then switched to the sysadm account (ABOVE) your /usr/adm/sulog
entry would look like:

SU  04/19/88  21:00 + tty 12 john-sysadm

Therfore the S.A(system administrator) would know that john swithed to sysadm
account on 4/19/88 at 21:00 hours

Searching for valid login names:   
-------------------------------
Type in-
$ who  ( command informs the user of other users on the system)
cathy  tty1  april 19  2:30
john   tty2  april 19  2:19
dipal  tty3  april 19  2:31
:
:
tty is the users terminal,date,time each logged on.dipal,john are valid
logins.   

Files worth concatenating(cat)
/etc/passwd file:                    
-----------------                     
The etc/passwd is a vital file to cat.For it contains login names of all
users including super user accounts and there passwords.In the newer          
SVR3 releases they are tighting their security by moving the encrypted
passwords from /etc/passwd to /etc/shadow making it only readable by root.
This is optional offcourse.

$ cat /etc/passwd
root:D943/sys34:0:1:0000:/:
sysadm:k54doPerate:0:0:administration:usr/admin:/bin/rsh
checkfsys:Locked;:0:0:check file system:/usr/admin:/bin/rsh
:
other super user accs.
:
john:chips11:34:3:john scezerend:/usr/john:
:
other users
:
$
If you have reached this far capture this file as soon as posible.
This is a typical output etc/passwd file.The entries are seperated
by a ":".There made be up to 7 fields in each line.
Eg.sysadm account.
The first is the login name in this case sysadm.The second field contains the
password.The third field contains the user id."0 is the root".Then comes the
group id then the account which contains the user full name etc .The sixth
field is the login directory defines the full path name of the the particlar 
account and the last is the program to be executed.          
Now one can switch to other super user account using su command descibed above.
The password entry in the field of the checkfsys account in the above example
is "Locked;". This doesn't mean thats its a password but the account
checkfsys cannot be accessed remotely.The ";" acts as an unused encryption
chracter.A space is also used for the same purpose.You will find this in many
UNIX systems that are small systems where the system administrator handles
all maintaince.  

Password aging:  
---------------
If password aging is active the user is forced to change the password at    
regular intervals.One may be able to tell just by looking at the /etc/passwd
file when the password is allowed to be changed and when it is compulsory to
change it.
For example the entry:

john:chips11,43:34:3:John Scezerend:/usr/john:

The password contains an extension of (,43) which mean that john can change has
to change the password atleast evert 6 weeks and can keep it for atleast 3
week.The format used is [password],Mmww.The M is the maxiumum number of weeks
password has to be change and m is the minimum interval password can be changed
and the ww is indicates when the password was last changed.

    Aging chart:
---------|-----------
Character|# of weeks
    .    |  0
    /    |  1
 0-9     | 2-11
 A-Z     | 12-37
 a-z     | 38-63
---------|-----------

From the above anyone can determine the number of weeks one can chnage the    
password.         

The (ww) is automatically added as to when the password was last changed .   

IF SHAWDOWING IS ACTIVE:
------------------------

If the shawdowing is active the /etc/passwd would look like this:

root:x:0:1:0000:/:
sysadm:x:0:0:administration:/usr/admin:/bin/rsh

The password filed is substituted by "x".

The /etc/shawdow file only readable by root will look similar to
this:

root:D943/sys34:5288::
:
super user accounts
:
Cathy:masai1:5055:7:120
:
all other users
:  

The first field contains users id:the second contains the password(The pw will
be NONE if logining in remotely is deactivated):the third contains a code of
when the password was last changed:the fourth and the fifth contains the 
minimum and the maximum numbers of days for pw changes(Its rare that you will
find this in the super user logins due to there hard to guess passwords)

  
/etc/options directory
-----------------------
The etc/options dir will consists of utilities available in the system.
Example:                  
-rwxr-xr-x   1 root  sys   40 april  1:00  uucp.name                
uucp standing for BNU

/etc/group
-----------
The file has each group on the system.Each line will have 4 entries separated
by a ":" . Example of concatenated /etc/group:

root::0:root
adm::2:adm,root
bluebox::70:

Group name:password:group id:login names
** It very unlikely that groups will have passwords assigned to them **
The id "0" is assigned to /

Sending and recieving messages:
-------------------------------
Two programs are used to manage this.They are mail & mailx.The difference
between them is that mailx is more fancier thereby giving you many choices
like replying message ,using editors etc.
Sending:
--------  
The basic format for using this command is:

$mail [login(s)]
(now one would enter the text
after finishing enter "." a period
on the next blank line)
$
This command is also used to send mail to remote systems.Suppose you wanted
to send mail to john on a remote called ATT01
you would type in:

$mail ATT01!john