port knocking

 In computer networking, port knocking is a method where externally open a port on firewall by attempting connection on prespecified closed ports. for example 1337 68 61 78

If we sequentially attempting connection on the above closed ports, then we shall get another port open by the firewall for us. 

We can do that by following ways:

knockd 10.6.0.2 1337 68 61 78

or 

knockd 10.6.0.2 1337 68 61 78

or 

for x in 1337 68 61 78; do nmap -Pn --max-tries 0 -p $x 10.6.0.2; done

Once it is done then start nmap scan again to see the newly found port. 

nmap -p- 10.6.0.2 -vv

Now we shall get a new port lets say 2021. 

Now connect on that port using nc 

nc 10.6.0.2 2021

ls

flag.txt 

cat flag.txt 

 

Avi