What tools do gambling or classifieds sites use to detect or know your using a vpn?
Thanks in advance.
The website you are visiting can know that you are using VPN through cookies, cache in your browser and also through your browsing fingerpro. You can read more about it from this site:
https://www.bleepingcomputer.com/vpn/guides/detect-vpn-use/I don't know if there are any special tools they use, but to me, it's very easy to know who is using VPN in some cases. If you notice a particular user who, each time they login to their account, appears in a new location with a different IP address from their last login, is that not an obvious sign of VPN usage?
If you are suing a paid VPN, you can set the location to the same address anytime that you want to connect online. Free VPN are the ones that is setting the address automatically.