From remote shell to remote terminal

If you like exploitation surely you've had your own reverse or connect-back shells. Set up a listening netcat, run the payload and boom: you get a shell back! Then you explore the box, start a program, want to stop it, and do Ctrl-C... no!!! You just lost your shell, because that interrupted netcat, not the remote process.

In this post we'll look at shells and terminals, from the most simple like this netcat with /bin/sh over the network, to a remote terminal emulator supporting terminal window size changes out of band. Think all the goodness SSH is doing for you, could we attempt something like it?

UDP scan with ICMP port unreachable and scapy

As you probably now, scanning UDP opened ports is painful because UDP is not connected, so you cannot rely on TCP SYN/SYN-ACK to find opened ports.

The ultimate network scanner nmap knows how to perform an UDP scan:

$ nmap -sU -p1-65535 <target>

You can add useful options such as -sV (probe open ports to determine service/version info). The scan is much longer than a TCP scan, but sometimes it works. Yes, sometimes. Recently I started a simple UDP server (with socat) on a random port and challenged myself to find it within the whole 1-65535 range: I appeared to be unable to find it with nmap (I'm probably misusing nmap).