But seriously--anything you might consider "subversive hacking" is illegal. I'm trying to think of an exception, and one really isn't coming to mind. It's legal to port scan people, but scanning the government or military is sort of asking for trouble.
It is easy to get caught if you don't know how to cover your tracks. I'm not going to give more details on not getting caught doing illegal things, because that's not how I roll.
I work in information security, and would love to point you in the direction of legal (but still cool) resources. One popular resource is the Offensive Security Metasploit Unleashed course http://www.offensive-security.com/metasploit-unleashed/Metas... -- It's well written and teaches you pretty much all there is to know about Metasploit, from basic usage to advanced scripting.
Hope that helps a little bit, and remember--the knowledge isn't illegal, but breaking into systems without propor authorization is. Don't throw away a bright future because you want to see what's on some random box.
What are you counting as "hacking"? Hacking together some encryption software to retain privacy from an intrusive government is subversive and, in many countries, legal.
My goal was actually to show (as you're rightly pointing out) that there are lots of cool security related hacks that one can do legally.
The poster, though, was asking about DDoS, form stuffing and otherwise "black hat" activities in relation to the law. You can't DDoS or exploit software on systems that you don't have permission to test, nor can you stuff forms to defraud advertisement providers like Adsense. Spamming email is illegal as well.
I'm not trying to argue the semantics of "hacker" and "cracker" and "script kiddie." Hacker News refers to hacker in its original sense, where as I perceive the poster to be asking about security related practices.
Now, LaBrea was unique, DMCA was a new law on the block and Tom Liston received a legal brief or opinion (I don't recall from whom) that stated that several states that were classified as Super DMCA States might actually consider LaBrea to be a reverse DDOS. It was sort of a stretch of the existing law, but, you could see how it could be applied.
The original intent of the SuperDMCA law was to prevent the anti-telemarketing devices from holding the line open when telemarketers called. Because of the way the old phone system worked, a flashhook would not disconnect two parties in case the person was on an older 1A switch and was trying to access certain services. This behavior moved over to 5ESS switches and even to this day, when someone calls, if they refuse to hang up and you don't have digital service, when you hang up you will not immediately get a dial tone. Briefly, the contention was that this behavior could prevent someone from calling 911 and could put the person in jeopardy. The rough comparison between the law and LaBrea Tarpit claimed Tarpit's behavior could constitute itself as a reverse DDOS - and Tom Liston stopped distribution of it. Of course, it was open source, but, by taking the stand that he wasn't distributing it, he was trying to protect himself from any legal liability.
I've dealt with the FBI on other DDOS attacks and I am in Florida, and I have told them that I have used Tarpit to defend against the DDOS. During one attack, they did offer to write an OIA as they wanted the data (political site).
So, even defending yourself against a DDOS could be illegal. :)
Hack via providing goods and services that consumers or businesses will pay for. You'll actually see a return on your efforts.
Any time I find something I immediately follow up with an email to the owner/administrator with all of the relevant information (including my IP address and contact information). The reactions have generally been quite positive (I've even gotten some complementary swag out of it).
Whether you will be prosecuted or convicted for those acts is a separate issue. Rule of thumb: if you cause harm/damage/bad things to happen, you will be prosecuted.