finding plagiarism - computer programming

Hi,

I've been doing some project evaluations and, looking through the list, I get stuck on how to find evidence to complete the evaluations for the projects that are plagiarized. This means that most of the time, I just leave plagiarized work to be evaluated by other people, even though I can see it's likely plagiarized and I'd likely be fine to evaluate that work if I had the evidence.

Today I clicked on a project that was pretty much exactly the same as one I evaluated a few days ago, I remembered it, so I know one of those people had to have plagiarised but I couldn't work out how to find the previous project given that it wasn't a direct spin-off. Also, many of the fish tank projects are clearly plagiarized but aren't direct spin-offs of whatever they've copied, but to fail someone, I'd prefer it if I could link back to a source to show where the code was originally from.

Some times I've seen some completed evaluations from other evaluators that have linked the plagiarized work as support for failing a project and I've wondered how those people are finding those original projects, given that people who are keen to plagiarize don't usually do direct spin-offs of the work they are copying, the copied work is not necessarily in the hot list, and it otherwise doesn't seem easy to remember where the projects might be from.

Does anyone have any guidance about the best way to find the source projects that people have plagiarised from, that's not going to take me a long time to look-up/implement ?