Fixing TLS 1.2 BEAST Attack

G5 Cyber Security

2 weeks ago

TL;DR

The BEAST attack exploits a weakness in older TLS 1.2 implementations. The best fix is to disable SSLv3 and TLS 1.0/1.1, and ensure you’re using modern browsers and servers with up-to-date security patches. If complete disabling isn’t possible immediately, consider browser extensions or server configuration changes to mitigate the risk.

Understanding the BEAST Attack

BEAST (Browser Exploited Authentication Status Technique) is a man-in-the-middle attack that targets Transport Layer Security (TLS) 1.0 and SSLv3 protocols, but can also affect some older TLS 1.2 implementations if not configured correctly. It exploits weaknesses in how these protocols handle block cipher encryption to potentially reveal cookies used for authentication.

Fixing the BEAST Attack: Step-by-Step Guide

Disable SSLv3 and TLS 1.0/1.1

These older protocols are inherently insecure and should be disabled on both your server and client (browser).
Server Configuration: The method varies depending on your web server (Apache, Nginx, IIS etc.). Here’s an example for Apache:
```
SSLProtocol off
SSLProtocol -All +TLSv1.2
```
Browser Configuration: Most modern browsers no longer support SSLv3 or TLS 1.0/1.1 by default, but you can check and ensure they are disabled in the browser settings (usually under Advanced security options).

Ensure TLS 1.2 is Enabled

Confirm that your server supports and prioritises TLS 1.2. Check using an online SSL testing tool like SSL Labs.
Server Configuration: In Apache, ensure the following line is present:
```
SSLProtocol +TLSv1.2
```

Use Forward Secrecy (PFS)

Forward secrecy ensures that even if your server’s private key is compromised, past communication remains secure.
Configure your server to use cipher suites that support Perfect Forward Secrecy (e.g., ECDHE).

Server Configuration: In Apache:

SSLCipherSuite ECDHE-RSA-AES256-GCM-SHA384:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-RSA-AES256-SHA384:ECDHE-RSA-AES128-SHA256

Keep Software Updated

Regularly update your web server, operating system, and browsers to the latest versions. Security patches often address vulnerabilities like BEAST.

Browser Extensions (Temporary Mitigation)

If you cannot immediately disable older protocols on the server, consider using browser extensions designed to mitigate the BEAST attack. However, these are not a long-term solution and should be replaced with proper server configuration changes.

Check Your Configuration

Use an online SSL testing tool (like SSL Labs) to verify that your server is configured correctly and does not support vulnerable protocols or cipher suites. Pay attention to the protocol support section of the report.

cyber security Considerations

While BEAST is less common now due to widespread adoption of TLS 1.2 and newer, it’s still important to ensure your systems are protected against it. Regularly review your cyber security posture and implement the steps above.