06. Nice netcat... - PicoCTF 2021 Writeup
There is a nice program that you can talk to by using this command in a shell, but it doesn't speak English
Category: General Skills | Author: Syreal | Points: 15
This is a very straightforward challenge. The description says it all. It simply wants us to enter that command into our terminal. Therefore we'll do just that.
nc mercury.picoctf.net 49039
What this does is actually ask a program called Netcat to listen to what the device at the other end of the URL given has to say in the port number provided. Netcat is a program that can handle network-related tasks. You can find more information on Wikipedia.
Interestingly enough, what we get is not actually a flag, but rather a bunch of random numbers. So, did we do something wrong? Actually no, there has to be some meaning behind the random numbers we got.
If you recall, when we go down to the barebones of a computer, it basically does its work in numbers. Can these numbers be related to that? Yes, in fact, they relate to a primitive, yet still used form of text encoding; called ASCII.
So let's quickly go to an ASCII to text converter and convert the numbers. You can use this tool if you prefer. When you enter these numbers, make sure to add zero padding to the front of the numbers that are less than three digits. ASCII run between 0 to 999, so it's essential to differentiate each character.
Amazing, the flag is right there!