nc

Netcat is a utility that can be used to create connections between two (or more) machines using specified ports. One machine listens for a connection which essentially opens a specific port whilst the other attempts to connect to it. Without firewalls the process is straightforward and allows for a simple connection between the two machines. Firewalls on either machine make it a little more tricky and require a few more steps.

emerge --ask net-analyzer/openbsd-netcat

nc -v hostname 80

nc -v hostname 1-1000

printf ‘HTTP/1.1 200 OK\n\n%s’ “$(cat index.html)” | netcat -l 1337

printf “GET / HTTP/1.0\r\n\r\n” | nc google.com 80

Reverse Shell

• A reverse shell is a remote access approach where you run administrative commands from one terminal while connecting to another server on the network. To get started, you need to enable the shell tool over a Netcat command by using Netcat reverse shell:

nc -n -v -l -p 1337 -e /bin/bash

nc 127.0.0.1 1337
$ type any command and you are connected to the reversed shell if it worked

Bind Shell

mkfifo /tmp/ncpipe
nc -lvnp 1337 < /tmp/ncpipe | /bin/bash > /tmp/ncpipe 2>&1

nc nr1 1337

Chat or Web Server

nc -lvvp 1337

nc localhost 1337   

Transfer files

nc -lvp 1337 < text_file_to_be_sent.txt

nc -w1 nr1 1337 > text_file_to_be_sent.txt

Send syslogs to a server

Quick References

<13> = user.notice <11> = user.err <14> = user.info <134> = local6.info <191> = local7.debug

How to Generate Specific Priority

• Example: send a local4.warning

  Facility 20 × 8 = 160 Severity warning (4)

  160 + 4 = 164

  • So:

  echo '<164>test message' | nc -u -w1 192.168.1.1 514

nc -w0 -u 192.168.1.102 514 <<< "testing again from my home machine"
echo hi |nc -w0 -u 78.69.211.116 1337