Go-Phish is a software to help find possible phishing websites.
The main idea is to use DNSTwist to generate a list of potential phishing websites from the URL provided by the user and, after that, use the concept of Levenshtein's distance to compare both website's source code and check how different they are. The website with the smaller distance calculated is then shown to the user.
If the returned percentage is very small, well, then maybe you should pay that website a visit 🧐