Re: unautherized access to unix systems?

From: Felix Zaslavskiy (felix@students.poly.edu)
Date: 01/20/03 

From: "Felix Zaslavskiy" <felix@students.poly.edu>
Date: Mon, 20 Jan 2003 08:10:37 GMT

> The number of holes available to someone who is on a machine is in
> general much greater than for someone not on the machine. Thus suid
> programs, which are not visible from outside, can often have holes. If
> the suid writer is careless and lets the program have root priviledges
> too long, then it can be eminantly attackable.
>
> Thus you can run buffer overflow attacks etc on internal programs.
> You can also install trojans and fake programs (eg ls in /tmp which when
> root runs ls and happens to have . in his path befor /bin, there you
> have root.) The usual rule of thumb is that if a good cracker gets onto
> a machine by whatever means, he can get root.

It does not matter how good a cracker with a user account is it all depends
on how many restrictions are placed on user account.

A machine with very little restrictions short of giving write privilages to
/etc/passwd to other users (similar to a development machine i run for
general learning purposes) would be easier to crack then a machine were
users are seen as potential attackers.

If a say read access to uses is denied to /etc directory and execution of
programs such as top,fstat, strace , netstat , gcc, is also denied in
addition to leaving very limited set of setuid programs around this would
make it very difficult to gain root with user account even for a pro
cracker.

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