It is critical to be aware of the possible repercussions for any action you take against a machine or network. There are legal boundaries that can result in a fine or imprisonment, depending on the laws and jurisdiction. For example, in the United States, the Computer Fraud and Abuse Act (CFAA) makes it illegal to access a computer without authorization. Don't always assume that the client authorizing the scope of your penetration test has the right to authorize you on every device. Companies can lease physical servers or rent virtual or physical space in a data center that they do not own, requiring you to get authorization from other sources as well.
There are also ethical boundaries to be aware of, which are different from the legal boundaries. Ethical boundaries can be a gray area for some people. For example, with...