How can I trust a proxy server?

bashix writes: "I am responsible to validate and distribute a huge number of proxy servers and TOR bridges in Iran. Many enthusiasts around the world are helping us by setting up proxy servers and sending us the info. But at the same time, I get a lot of suspicious submissions. So I want to ask Slashdot readers, how can I make sure that a given proxy server is valid and is not in fact set up by Iranian Gov. or people with less than honorable intentions?"