The word Hacker has many meanings. I have generally aligned myself with the older meaning, described in Steven Levy's book "Hackers: Heroes of the Computer Revolution".
However, I have occasionally engaged in activities which I have referred to as "Hacks", involving external websites or companies, although "pranks" might be a better word. This is really a page about some of my more prankish / immature behavior. As I've gotten older, I've done less of it.
AlexBot & PatBot
In the early 90s, there used to be a jeopardy IRC channel that had a running game of Jeopardy. It was run by a bot called AlexBot (named after Alex Trebek) and it used a large database of questions which were crowdsourced. I thought it would be interesting to write a 'cyborg' IRC client that would automatically spit out correct answers to the questions when it knew them. It knew them because it understood the Q/A format the game used, and stored the correct answers to questions. As you played the game, the same questions would reappear, and eventually you would have seen most of them before. As I played with the cheat-bot, it became pretty obvious to me that *all* the top contenders on the IRC channel were fellow cheats (they exhibited the same tells that I did, such as submitting matching misspellings).
My interest in the Jeopardy channel eventually led me to create my own game channel for the Wheel of Fortune. I designed two bots, PatBot and VannaBot which worked in tandem to host a Wheel of Fortune game that ran much like the one on the TV show. Pat would facilitate the spins and vowel buying and Vanna would periodically display the puzzle's current state. There was a set of random prizes which included a set of Vanna's Chromosomes. I eventually ported this code, pretty much verbatim for the "Wheel of Cheese" game which was quite popular on The Palace, the virtual chat environment that I worked on in the mid-late 90s.
Back in the late 90s, one of the first instant messaging services was called ICQ, it was created by an Israeli company, Mirabilis. ICQ used a series of sequentially rising ID numbers, called UINs to identify users, and these numbers were visible to other ICQ users. Every time a new user signed up for ICQ, they would get the next number in the sequence.
At the time I started using ICQ, these numbers were in the (best I can recollect) 400-500k range. I decided it would be cool to obtain the number 1,000,000 (one million) when it rolled around. I reverse engineered the ICQ protocol (which was horribly insecure) and wrote a Perl script which continuously predicted when a particular target number (such as 1,000,000) would be given out (it did this by allocating dummy accounts and looking at the UIN received and the current time and comparing this to the last one it had allocated). As a result it would be able to estimate when in the future the target number would be given out. I would then divide that time in half, and repoll at that point, to get an increasingly accurate assessment. The 'ol Zeno algorithm.
Anyway, when we were within a few seconds of the predicted time for 1M, my program automatically signed up for a bunch of ICQ accounts in a burst, grabbing as many numbers as it could until the target number was obtained or exceeded.
I used this technique to obtain a number of desirable "vanity" ICQ numbers, which I used myself, and gave away to friends (Palace employees, mainly). These numbers included the much sought after 1M, as well as 999,999, 1,111,111 and so on. Unfortunately, the same insecurities that enabled me to grab these numbers enabled others to steal them from me. Easy come easy go! Incidentally, as the 1M mark approached, I remember there was an obvious jump in UID allocations, which meant that I wasn't the only one trying to grab that 1M.
In 2010, when FourSquare was still new, I did some examination of their (partially documented) APIs, found some holes, and did a big land grab, making myself mayor of such landmarks as The Statue of Liberty, Mt Rushmore, The Taj Majal, and The North Pole. Did a few other fun things with it as well. After a few days I stopped and wrote about my exploits in my blog post entitled Mayor of the North Pole.
This got some (negative) coverage on TechCrunch and some (positive) coverage in The LA Times. FourSquare's Dennis Crowley came over to my blog and was very nice about it.