JakeGould did a great job of framing this in practical terms and avoiding the "moral" angle.  So I'll just add a little about the "moral" angle.

The Stack Exchange has wrestled with the grey line virtually since its inception.  There are a number of categories of issues. 

**Blatantly illegal activity.**  The SE has official policy in this area.  We don't answer questions that enable it.  That includes things like software piracy and circumventing protection against theft of services.  The SE is also pretty vigilant about protecting and honoring copyrights.

**Civil contract issues.**  The grey line runs through terms of service and user agreements.  Half of the members believe it is unethical to facilitate violation of such contracts between a publisher/provider and the user.  The other half believe it isn't our role to police such contracts and we should share technical information regardless of how it might be used.  

The merits have been argued for years and the SE has generally avoided taking an official position.  The exception is Hackintosh, which has been a recurring, high volume topic; the SE made an administrative decision to not support those questions.  Any other questions of this type stand a 50/50 chance of being answered or closed, depending on who sees them (assuming they're otherwise good questions).

**Intellectual property restrictions.**  Many users (particularly those who don't create software  or web sites for a living, or work in IT), don't think in terms of intellectual property; that someone invested time to create it, and relies on it for their livelihood.  Or they may be aware of it but consider certain big corporations to be undeserving of all of the revenue from their products.  So we get questions about circumventing restrictions on intellectual property.  This may seem different from piracy when the question is about information on a public web site that is locked or protected against routine copying.

Our user base with the knowledge to answer is generally pretty good at closing those, or at least challenging the OP for a legitimate justification.  But there are often users in the knowledge-sharing camp who see no problem with answering.  This should typically fall under the guidelines of prohibited questions, but sometimes aren't obvious to all users.

**Controls by repressive governments.**  These tend to be on the other side of the grey line.  There is no official policy on these.  Many/most users view answering how to circumvent these as the morally correct side.  But it's a slippery slope deciding what's repressive and what's legitimate, and which countries are repressive and in what ways.  Some people consider any restriction by any government as repressive, and opinions vary as to which countries' governments are "good" and "bad".  

For example, not long ago, there was a question about getting a laptop onto a plane past the TSA inspection.  Yes, the TSA rules tend to be ridiculous, but do you really want to potentially help a terrorist get a bomb on a plane?  Questions are public, so regardless of the merits of the OP's needs, they aren't the only ones with access to the answers.

**Computer security.**  This encompasses issues like accessing a computer without the password or malicious attacks.  Here, the ethical question is in how the information might be used, not necessarily in the question, itself.  There are legitimate uses for the information, like getting into your own computer, learning about computer security, and developing protections against malicious activity.  There are also obvious unethical uses.

I'm not aware of any official guidance, but there is precedent.  Generally, bypassing passwords has been an acceptable topic, perhaps because it is such a common innocent requirement and the information is readily available, anyway.  I've seen a few questions on the theory of how various malware works, how to get malware samples, and how to conduct specific types of hacking.  

The responses often reflect the question.  These generally don't raise concern when the question is asked about accessing the user's own system, or an academic exercise using commonly available tools.  However, questions that don't express a "legitimate" need or intent often get push-back.  This isn't so much due to any official guidance as readers exercising common sense.

**Bottom line:**  the SE has very limited official guidance on ethical issues; it's tangential to the technical nature of the sites like Super User.  So for much of the ethical territory, there is no official "should or should not".  People will apply their own moral compass.  Hopefully, vigilant users will notice questions or answers that are ethically suspect or potentially dangerous.  They can comment on the post to educate and warn, raise the issue here or on the Ask a Super User Moderator chat, or flag or vote to close or delete, depending on rep.