Securing Your Web Application with Cloudflare WAF: Blocking Malicious User-Agents

As a website owner, it is essential to protect your site from malicious activity such as cross-site scripting (XSS) attacks, SQL injections, and other malicious activities that can compromise the security and stability of your website. One of the ways to achieve this is by configuring Cloudflare Web Application Firewall (WAF) to block malicious user-agents.

A user-agent is a string of text that is sent by a user's web browser to a website's server, indicating the browser's name, version, and operating system. By analyzing user-agents, website owners can determine what type of device is accessing their site and block specific user-agents that are potentially malicious or suspicious.

To configure Cloudflare WAF to block malicious user-agents, follow these steps:

1. Log in to your Cloudflare account and select the domain you want to configure.

2. Navigate to the Firewall tab and select the WAF Rules section.

3. Click the "Create a Custom Rule" button.

4. In the "Custom Rule" field, enter the following code to block all user-agents that contain "malicious" in their string:

   user-agent !~* "malicious"
   

5. Save the rule by clicking the "Save" button.

Once you have created the custom rule, Cloudflare WAF will block all requests that contain "malicious" in their user-agent string. To add more user-agents to the blocklist, simply add another line to the custom rule with the desired user-agent string.

Here are some examples of potentially malicious or suspicious user-agents:

1. "Havij" - This user-agent is commonly associated with SQL injection attacks.
2. "curl" - This user-agent is often used by automated scripts and bots to scrape website content.
3. "sqlmap" - This user-agent is commonly associated with SQL injection attacks.
4. "BlackWidow" - This user-agent is associated with web spidering and crawling.
5. "HTTrack" - This user-agent is associated with website copying and mirroring.

While blocking malicious user-agents is an effective way to secure your website, it is important to note that not all user-agents associated with malicious activity are clearly labeled. As a result, it is important to regularly review your website logs and keep an eye out for any unusual traffic patterns or requests.

In conclusion, configuring Cloudflare WAF to block malicious user-agents is an effective way to secure your website and protect it from malicious activity. By following the steps outlined in this article, you can help ensure that your website remains secure and stable.