Once upon a time, for the IT Security course, we decided to change SSH so that at any 3rd attempt it would allow an attacker in, stopped allowing other attacker

Once upon a time, for the IT Security course, we decided to change SSH so that at any 3rd attempt it would allow an attacker in, stopped allowing other attackers in, and at the same time that we tried to have a kernel module that intercepted ICMP Echo's and gave the SSH session keys in it's reply (inspired on something similar on Phrack). We managed to get close to that, but we didn't get the session keys part :(