To protect proxy servers from being hacked, security measures like encryption, regular software updates, strong authentication protocols, and access controls can be put in place. If a hacker successfully breaches a proxy server, it could result in unauthorized access to important information, interception of communications, introduction of malware, and data breaches. Users can detect a compromised proxy server by watching for suspicious activity, sudden performance issues, or by performing security checks. If security is a top priority, other options like using a virtual private network (VPN), setting up firewalls, or utilizing secure browsing methods like Tor browsers can also be considered.