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25 May 2020

F5 WAF – Good Protection



The first time I read about Web Application Firewall (WAF) I thought it would be difficult to install and configure because it’s really different from network firewall. Network firewall policies has mainly IP addresses and services. It’s easy to understand and configure. However, WAF has mainly file types, URL, HTTP methods and headers. It seems more complex than network firewall. Nevertheless, I think the most important thing is to start configuring a basic policy. We have to start small, but most of all, start. We are going to realise that a basic security policy will be a good protection. A basic security policy requires little administration effort. A basic security policy is going to protect a high percentage of applications.

Progressing with application security using the BIG-IP ASM system

We should enable Attack Signatures in a basic security policy for a good protection. An attack signature is a rule or pattern which is able to identify a particular attack. These signatures are updated by the F5 threat research team daily with the new vulnerabilities discovered. The F5 ASM uses these signatures to each HTTP request and response to detect and block known attacks. In addition, the Transparent Enforcement Mode is also really useful because we can apply a security policy in transparent mode to detect attacks but they are not going to be blocked. It’s really useful because we can know how many attacks and what kind of attacks web services are receiving.

Attack Signature List

IP Intelligence is another interesting useful feature for a good protection. IP Intelligence is a subscription-based database where there are lots of malicious IP addresses. Updating manually a blacklist is really difficult because malicious IP addresses are constantly changing. Therefore, configuring IP Intelligence to block malicious IP addresses is easy and a best practice. On the other hand, it’s also a best practice to configure the IP Geolocation feature, which is another database of IPv4 and IPv6 addresses. This database can be used to identify the origin of traffic and, at the same time, we can deny access to a particular country of origin.

IP Intelligence
 
A common attack vector is confusing web servers, web applications, and security products using malicious content hidden in HTTP requests that web servers and simple HTTP proxies often fail to detect. As a result, Protocol Compliance must be mandatory in WAF security policies. For instance, HTTP Protocol Compliance will check Content-Length in POST requests as well as whether there is no Host header in HTTP/1.1 requests. You can see all the validation checks in this K10280. Moreover, Protection from Evasion Techniques, such as using ../ to navigate to a parent directory of interest, is also recommended.

HTTP Protocol Compliance
 
Finally, there are two more security features really useful for a good protection. One of them is Protection from Parameter Exploits - Blacklisting. This feature parses parameters and it validates the values against signature and metacharacter policies to identify known exploit patterns. The other security feature is Threat Campaigns which is a subscription service for Advanced WAF that provides a set of data to evaluate whether incoming requests are malicious.

Threat Campaign
 
Regards! Stay at home! Start protecting your web applications, but most of all, start!

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