De-anonymizing Proxies or VPNs

[Piholasimam]

Hello all,

I wanted to see if anybody had feedback about any methods to de-anonymize something(someone) that is using a proxy(or VPN). I'm not well versed in networking, (bear with me). But my goal is to stimulate a discussion about what is technically possible and what is impractical. I have already done some thinking about this. Perhaps if you own the proxy, surely you can log the clients real IPs correct?

Or maybe some other method makes more sense.

Thanks for any feedback,
Pi