If you got it from someone that you don't know or don't trust, which is what it sounds like, or if you got it from someone that you know & trust, but they've told you that they're passing the script along, DON'T use it.
You should only use scripts that are from people that you know & trust. Additionally you should only use scripts, where you know what they do.
You can load a script into notepad, and it'll show as a text file. At that point if you can decide if you understand the code or not. If you're still not sure, please post the code here, remembering to use the code tags.
That is the safest and best way to get us to check a script.