HI,
I have a Centos linux box and there is interface connect to internet.
I stop the iptables in this box .
After a few day , I find the linux box have been hacked and install some perl script into the box .
Could anyone tell me how the hacker can login into the centos box without knowing the root passwd ???
How can they do it ?? please advise in detailed step...

Thank

Pff, it can range from infected client computer (the one that you used to login into the centos box) to brute-forcing you password... Ofcourse, an exploit is also possible.. What other services run on that box... Or it could be a man-in-the middle..

The only thing for sure from your question is that you made at least one mistake (and I'm telling you this so you can learn, not to critisize): 'root' logins in ssh shouldn't be enabled.. Use a normal account and 'su' or 'sudo' instead (with password)

Maybe give us the content of the perl script?

HI,
Actually, I want to know how Ican hack a linux box without using passwd ......Please advice ....

Then I advise you to find another board. This question is in violation of the LQ Rules.

I think when you tell "I can hack" is in a generic sense, since it is your Linux system that has been allegedly hacked, isn't it? Anyway, no one here can provide detailed step by step description of the process, since it would really be in violation of the aforementioned LQ rules. We can only provide links and citations of such techniques, as Smokey_justme already did, in order to enhance security of Linux systems and implement counteraction. Other members are kindly invited to maintain this course and not derail from the topic.

If you have a founded suspicion that your system has been hacked and you need help to restore your system to a safe configuration, you may consider to move your thread to the Linux - Security forum (please, use the report button to ask for moving).

Reverse shells, compromised credentials, brute force, the list goes on and on...

See Compromise, breach of security, detection

Thanks to unSpawn, to whom we are grateful.

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