Head over to Hack-Test and check it out! Do comment on upto what level you made it! If you’re finding it tough, do check the hacker forums for tips, hints and possible spoilers. Enjoy hacking!. Thanks Anurag for the tip.
PS: Incase you’re wondering how I fared, well I did rather badly, still stuck in level 3.
PPS: Incase you landed here searching for some way of breaking into other systems, get your definition of a hacker right, you idiot.