How to check the code for license purity?

Question

Law in IT

Hello everyone,
I have seen in articles more than once that the finished product / binary of company X was scanned and a lawsuit was filed against it for using someone else's code or for violating the license agreement.
What are these programs and how to find them?
At the current place of work there is a certain code that was written X years ago and no one knows whose it is (100% of the company or not).
How can you solve the problem of checking the code?

Answer 1

Well, if you look at it like that, then even a banal sorting with a bubble is already drawn to "foreign code" and "license violation" ...