It is possible to make a full connection to a system with a poor TCP initial sequence number and perform a blind TCP spoofing attack on them. This kind of attack was the most popular one in the '90s when people used rlogin, which is a remote shell client (like SSH) that allows users to log in on another host via network, communicating using TCP port number 513. In December 1994, Kevin Mitnick had supposedly used this attack to break into Tsutomu Shimomura's (computer security expert, currently CEO of Neofocal Systems) computers. Luckily, almost nobody uses rlogin anymore. However, blind TCP spoofing may still be effective for HTTP requests.

Now, you might be surprised with the log. What does the good luck comment mean? Well, there is an estimated difficulty of how hard the system makes blind IP spoofing (where 0 is the easiest).

These comments are based on this index, starting from trivial joke to easy, medium, formidable, worthy challenge, and finally ending with good luck.