WordPress Security Explained
WordPress Security Explained
Posted By Gregory

Why reCAPTCHA does not protect WordPress against bots and brute-force attacks

Using reCAPTCHA for WordPress login form is a bad practice and does not protect WordPress from being hacked by bots and hackers

What is reCAPTCHA, anyway?

Google’s reCAPTCHA is a human verification mechanism that created and maintained by Google as a free web service. WP Cerber supports reCAPTCHA for WooCommerce and WordPress forms as an anti-spam feature.

Why does reCAPTCHA not protect WordPress from bots and brute-force attacks?

It’s possible because WordPress has three authorization methods that enabled by default. That means hackers can exploit three entrances on any WordPress powered website. The first one is using the default WordPress login form. Two other methods are invisible for you but known for hackers and specialized software that hackers use. Cybercriminals use them for obtaining users’ passwords and consequently to get access to the WordPress Dashboard with admin privileges.

Any captcha-based mechanism, including reCAPTCHA, can protect WordPress against a brute-force attack to an ordinary login form only. The other two WordPress authentication methods are still unprotected. Why? Because reCAPTCHA is developed to protect websites from robots via a human verification mechanism. Hackers are not robots even if they use botnets. That’s why reCAPTCHA does not protect websites from being hacked.

You must not use any plugin that adds reCAPTCHA to the WordPress login form to protect your website from brute force attacks

I see plenty of plugins that offer using reCAPTCHA to protect login form. I have a question for you: do those plugins protect your website completely including the following two methods like WP Cerber does.

  1. Cookie-based authorization
  2. XML-RPC authorization

Does it mean reCAPTCHA useless?

Nope. reCAPTCHA can be successfully used as a spam-prevention mechanism for registration, contact, and password reset forms. Vital parts of WordPress must be protected with a specialized security solution only.

How do I protect my website from spam?

To protect WooCommerce and WordPress forms, WP Cerber Security offers two options

  1. Cerber antispam and bot detection engine, follow the instruction: Antispam protection for WordPress forms
  2. Using reCAPTCHA, follow the instruction: How to set up reCAPTCHA.

How to bypass reCAPTCHA

Is it possible that bots can solve reCAPTCHA without a human? Sounds unbelievable but they can do that by using an interesting method. The method is based on using voice captcha called Audio Challenge and one of those online speech recognition services like Google Speech Recognition API. A hacker takes an audio file with voice captcha generated by reCAPTCHA and then recognize it with a speech recognition service. Is not it brilliant?

This method has been discovered back in 2012. Fortunately, this method is not exploitable in real circumstances  – when Google service identifies multiple attempts to solve the captcha from the same IP address, the voice captcha is changed into a more complex voice that cannot be identified using this approach. So, to successfully use this method hackers have to use a lot of IP addresses. To achieve that hackers can infect a significant amount of mobile devices with malicious software. But there is a question. Is the ability to post spam comments or register with a fake name on a website worth it? It’s easier to hire a bunch of guys from a poor country to do that manually in a bulk mode.

Want to know more? Subscribe to the Cerber’s newsletter.

Have any questions?

If you have a question regarding WordPress security or WP Cerber, leave them in the comments section below or get them answered on the community forum.

Spotted a bug or glitch?

We’d love to fix it! Share your bug discoveries with us here: Bug Report.

I'm a software engineer and team lead at Cerber Tech. I started coding in 1993 on IBM System/370 and today software engineering at Cerber Tech is how I make my living.

View Comments