How to hack Linux by breaking the root password on RHEL OS

Passwords are the most basic security of a computer system. In the case of linux operating system it is the root password. If you have the root password you own the system by all means. Today I am discussing about how to break the linux root password and of course the countermeasures for such a hack.

The following hack is tested on RHEL OS and you needed physical access to the machine to perform this.

1. Boot your system , at the time of booting press any key to access the GRUB Menu.
2. Press 'e' to enable and move to the second line which starts with the kernel.
3. Again press 'e' again to edit the kernel parameters.
4. Add 'a' at the end of the line and press enter (without quotes). This will start the system in single user mode instead of default run level.
5. Now press 'b' to start booting in single user mode.
6. Now the system will start in single user mode and use the passwd command to change the root password. Sometimes passwd command will not work in that case assume that the SElinux is in enforcing mode.So you have to first disable it and change the password using passwd. To disable SElinux enforcing mode use setenforce 0 command.
7. After changing the password switch to GUI mode using init 5 command and start using the newly assigned root password.

This hack can be easily prevented by enabling password to access  single user mode.To do that edit/etc/rc1.d/S99single file and add  exec /sbin/sulogin before exec init t1 S statement. Now you have to give root password to access single user mode..

Hope you enjoy this hack.

Source: 
http://www.opentech4u.com/2013/03/how-to-hack-linux-by-breaking-root.html

»»  Read more...

Resetting LINUX OS root password without login

Alright folks, let's say you've lost your root password, or simply cannot log in as root after a hard drive install, and have no privileged users on your system. I'm about to show you how to get back in the game as root with a quick and dirty password-change hack.

For this tutorial, everything that is italicized is a user action. Anything in <angle brackets> is a keystroke. If it has a + beside it, it means press the keys at the same time.

## Changing the root password:

=======================================================================

1. Reboot your computer. Wait for the grub screen... Press <ESC> when you're prompted.
2. Highlight the first option.
3. Press <e>.
4. Highlight the kernel line.
5. Press <e>.
6. Press <TAB>. You'll get an error message.
7. Press <ESC>.
8. Press <e> again.
9. Using your arrow keys, scroll back and change ro to rw
10. At the end of the line add: init=/bin/bash
11. Press <Enter>
12. Press <b>
13. Type at the prompt: passwd root
14. Enter the new password twice.
15. Press <CTRL>+<d> to cause a nice Kernel Panic. This will cause your system to hang.
16. Press and hold your power button till it shuts down. Power back up and let it boot into BackTrack normally.
17. Log in as root with your new password.

Source:
http://www.backtrack-linux.org/forums/showthread.php?t=799

»»  Read more...