On 19 Jul 2002, Jaishankar Krishnan Iyer wrote:
The box did NOT run any firewall etc. The next day what we found was, it would NOT allow us to login at all. At the login prompt , when one tried to login as any user or even "su" it would just jump back to login prompt.
did you try to login as su or as root?
Could i get some hint as to which are the likely files which i could look into which could cause this problem. This would help us further in the penetration test which we are conducting.
have a look at your pam.d/* files. also, by removing some groups, you may have disabled logins. You'll have to experiment to find out.