Virus in linux????????

["Rahul Jindal" <rahulj@xxxxxxxxxxxxxx>]

Hello all,
something really strange happened today, strong enough to shake me, so don't
mind the crooked language below.

we have linux 6.2 installed on the computers in our lab. the admin logged
onto a computer 8:30 in the morning and left the login in the root user a/c.
after sometime we discovered that the system won't just let us perform the
admin tasks. we could still login with other a/c names and work on the
computer as normally as ever. we even started the X. only the admin
functions wouldn't work.

if we try su, it says the user root does not exist. the files such as
/etc/shadow and /etc/password /etc/issue are apparently as always.

THE MOST STRANGE PART IS THIS:

1. IF WE TRY TO LOGIN AS ROOT THE FOLLOWING HAPPEN

    IF THE PASSWORD IS THE SAME AS THE ADMIN HAD SET IT - THE SCREEN WOULD
SIMPLY CLEAR, WITHOUT GIVING ANY MESSAGE.
    IF WE ENTER A WRONG PASSWORD, THE EXPECTED login incorrect APPEARS.

    apparently the "virus" scans for the actual password.

2. IF WE TRY TO RESTART THE COMPUTER BY DOING THE FOLLOWING
        A) PRESS CTRL-ALT-DELETE
        B) reboot
        C) SHUTDOWN -H 0
THE FOLLOWING MESSAGE APPEARS

"You don't exist anyway. Go away".

What is this going on?
The whole system has gone read-only. I call it a "virus" because there was
no person who cud do this, those who were are the beginners in linux
practising commands such as ls.

Any clue or remedy is desparately awaited.

Waiting

Rahul