Why do some bot detection tools miss bots that hide behind VPNs and proxies?

Bots can hide behind VPNs, proxies, and location masking to make their network traffic look normal. A tool that only looks at IP reputation or a single network signal will often miss them. BotRefund uses the DNS Challenge Blocked check as one of 106 independent checks and feeds it into a prediction AI that looks at the complete pattern. That cross-checked approach is why it can catch sophisticated evasion without jumping to conclusions.