Controlling XML-RPC Access to Prevent Brute Force and DDoS Attacks

To control XML-RPC access and prevent brute force and DDoS attacks, the most effective measures include disabling or blocking access to the xmlrpc.php file, implementing strong authentication methods, and applying rate limiting and request filtering.

Key strategies are:

• Disable or block xmlrpc.php: Completely blocking access to the XML-RPC endpoint (xmlrpc.php) is the simplest and most effective way to stop attacks exploiting it. This can be done via security plugins, .htaccess rules, or server configurations. For example, adding rules to .htaccess to deny access or using WordPress plugins that disable XML-RPC functionality can prevent brute force and DDoS attacks that target this file.

• Use strong authentication: If XML-RPC functionality is necessary, avoid weak authentication methods like HTTP Basic Auth over plaintext. Instead, use token-based authentication such as OAuth2 or JWT, which provide fine-grained permission control and reduce exposure to session hijacking. Mutual TLS (client SSL certificates) offers the highest security but is more complex to manage.

• Rate limiting and request filtering: Implement strict rate limiting on XML-RPC requests to prevent brute force attempts that try thousands of username-password combinations. Security plugins like Shield Security offer granular access control by IP, user role, or request type, and can filter or block malicious XML-RPC requests.

• Keep software updated and monitor logs: Regularly update WordPress core, themes, and plugins to patch vulnerabilities. Monitor access and security logs for suspicious XML-RPC activity to detect and respond to attacks early.

• Disable unnecessary XML-RPC features: If you do not need XML-RPC, disabling it reduces attack surface, prevents spam comments and pingbacks abuse, and lowers server load caused by excessive XML-RPC requests.

• Mitigate XML-specific attacks: Protect against XML External Entity (XXE) attacks by disabling external entity expansion in XML parsers used by XML-RPC implementations.

In summary, the best practice is to disable XML-RPC entirely if not needed; otherwise, secure it with strong authentication, rate limiting, and request filtering while keeping the system updated and monitored. Blocking or disabling xmlrpc.php is the quickest and most reliable defense against brute force and DDoS attacks targeting XML-RPC.