What’s a Internet Software Firewall (WAF)?


An internet utility firewall (WAF) sits between net functions and the web. It screens inbound visitors and filters malicious requests earlier than they attain the doubtless weak utility. This text explores WAFs, how they work, the most well-liked and efficient examples, and why you must think about using a WAF to guard your website or app from cybercriminals.

Does Your Internet App Want a WAF?

Eventually, each web site, app, and API is focused by malicious bots or their cybercriminal operators. If it’s on-line, it’ll be attacked. Vulnerabilities might be exploited, knowledge might be stolen, net pages might be defaced, and malware might be injected. An internet utility firewall (WAF) works alongside different safety measures to defeat dangerous actors and preserve websites and apps secure. 

When you don’t use a WAF, you rely on the net app to repel assaults. That will work within the quick time period, however a WAF supplies a further layer of protection that may be dynamically up to date to guard in opposition to rising threats. WAFs are an efficient and helpful protection in opposition to the most typical assaults in opposition to net apps and APIs.

How Does a Internet Software Firewall Work?

A WAF is a reverse proxy. It intercepts inbound HTTP requests and inspects them for patterns that point out an assault. If an assault is detected, the request is dropped earlier than it reaches the online app. Reliable requests are handed by way of the WAF to the app, which responds as normal. 

You may consider a WAF as a filter. It absorbs all incoming net visitors and removes any that could possibly be dangerous, offering the app with a stream of pre-vetted, authentic requests. 

One of many foremost benefits of a WAF is that it may be up to date rapidly in response to new threats. Think about what occurs when a difficult zero-day vulnerability is found in an online app. It won’t be attainable to launch a patch instantly, and even when it have been, there’s a delay between patch launch and updating, particularly for apps with many cases. 

WAF customers can, nevertheless, rapidly add new guidelines to filter inbound requests that would exploit the unpatched vulnerability. This capacity permits companies to maintain net app customers and their knowledge secure with better effectivity and suppleness. 

Does a WAF Exchange a Community Layer Firewall?

WAFs complement community firewalls and supply further safety however don’t change conventional community layer firewalls. An internet utility firewall works on the utility layer, Layer 7 within the OSI mannequin. It intercepts HTTP knowledge however can’t monitor and filter knowledge protocols used at decrease ranges. 

In distinction, firewalls equivalent to iptables sometimes function on the community and session layers (Layers 3 and 4). They work with low-level protocols equivalent to TCP and UDP, however not higher-level protocols equivalent to HTTP. 

Some fashionable firewalls cowl a broader vary. For instance, AWS Community Firewall can monitor and management Layer 3–7 community visitors, combining the performance of a community layer firewall and a WAF. Nevertheless, customers ought to confirm the particular capabilities of every firewall earlier than counting on it to guard their net functions. 

Threats Internet Software Firewalls Forestall

Internet utility firewalls defend in opposition to many various kinds of assaults generally used in opposition to net apps. These embrace assaults that conventional community firewalls can’t intercept, together with:

  • Cross-site scripting (XSS): malicious code injection into net pages.
  • Cross-site forgery: an assault that forces an authenticated consumer to hold out undesirable actions.
  • SQL injection: the injection of SQL code, which is then executed by the positioning’s database.
  • Cookie poisoning: session hijacking utilizing solid or intercepted cookies.

Many WAFs additionally present some safety in opposition to distributed denial of service (DDoS) assaults. As a result of all visitors goes by way of the WAF first, it may be rate-limited and malicious floods of visitors could be filtered. Nevertheless, a WAF is unlikely to guard an online app in opposition to a large-scale volumetric assault as successfully as a devoted DDoS mitigation service

Moreover, some WAFs can be utilized to implement protections normally carried out on the community layer. Many WAFs enable customers to add lists of IP addresses to dam. They may also be used to dam visitors sources which are thought-about prone to trigger points. For instance, AWS WAF curates a managed algorithm for blocking visitors from TOR and VPNs, and different WAFs supply comparable performance. 

What Are the Forms of Internet Software Firewall?

All net utility firewalls serve the identical basic function, however there are various internet hosting and operational fashions. These could be divided into three broad classes:

  • Community-based WAFs are normally hosted on devoted {hardware} in knowledge facilities near the appliance they defend. Community-based WAFs are sometimes used to guard giant, high-traffic functions the place low-latency connectivity is a precedence. They’re the most costly WAF kind and essentially the most complicated to handle and preserve.
  • Host-based WAFs are built-in into the software program they defend and could also be hosted on the identical {hardware}. For instance, many WordPress plugins combine a host-based net utility firewall with the CMS. This strategy has the advantage of flexibility and ease of use, but it surely may end up in lowered efficiency if the host lacks the assets to run the WAF and the app at peak load occasions.
  • Cloud WAFs are managed companies hosted on cloud platforms. They’re the simplest to make use of and handle. The cloud supplier manages the software program and underlying {hardware}. They’re additionally chargeable for deploying guidelines and insurance policies for filtering threats, together with updates for rising threats. Cloud WAFs present an inexpensive degree of customization, efficiency, and uptime, however they will not be the most suitable choice for companies that want extra management over their firewall.

WAFs might also be categorized by whether or not they function on a blocklist or allowlist mannequin. A blocklist selectively disallows connections that match an undesirable sample, whereas an allowlist permits connections that conform to a fascinating sample. 

There are benefits to each approaches. Blocklists enable safety professionals to focus on identified malicious connections. In distinction, allowlists can block all connections that don’t match a fascinating profile. Allowlists are efficient and require much less upkeep, however they will not be appropriate for functions supposed to be accessible to as many customers as attainable.

In style Internet Software Firewalls

There are dozens of WAFs to select from. Though they provide comparable core performance, they differ in focus and options. To conclude this text, we’ll have a look at 4 broadly used WAFs.


ModSecurity, or ModSec, is an open-source WAF initially developed as a module for the Apache net server. It subsequently advanced right into a cross-platform WAF for Apache, Nginx, and Microsoft Web Data Providers (IIS). 

ModSecurity secures net apps utilizing a algorithm to find out which connections to simply accept and which to dam. These could be custom-made by the consumer, however there are a lot of pre-made rule units. One of the broadly used is the OWASP ModSecurity Core Rule Set, which detects the ten most widespread assaults, together with SQL injection, cross-site scripting, and native file inclusion. 


AWS WAF is a managed cloud WAF supplied by Amazon Internet Providers. It’s straightforward to configure and deploy, and customers pay just for the cloud compute assets they eat. Customers can create their very own firewall guidelines, however AWS additionally supplies Managed Guidelines, pre-configured rule units that cowl a particular vary of threats. Primary managed guidelines units are free, and extra specialised units are made obtainable on the AWS Market, together with an OWASP High Ten set. 

Along with normal WAF options, AWS WAF additionally supplies bot management performance, which permits customers to observe bot visitors and block or price restrict visitors from bots that use extreme visitors. 

Watch Introduction to AWS WAF and Protect and Defending API Gateways with WAF Guidelines to study extra about AWS WAF. 

Azure Internet Software Firewall

Azure Internet Software Firewall is a cloud WAF supplied by Microsoft’s Azure cloud platform. It supplies a lot the identical performance as AWS WAF, together with managed rulesets that defend in opposition to the OWASP High Ten and different widespread threats. 

Cloudflare WAF

Cloudflare WAF is a part of Cloudflare’s vary of CDN and safety companies. It’s a cloud WAF built-in with Cloudflare’s international community, offering managed and {custom} guidelines, protections based mostly on machine studying, and fast deployment of guidelines to guard from rising zero-day vulnerability threats. 

Internet Software Safety and Compliance with KirkpatrickPrice

An internet utility firewall is one element of an efficient safety and compliance program. KirkpatrickPrice supplies a spread of companies to assist companies safe their infrastructure and adjust to regulatory frameworks and requirements, together with compliance audits, penetration testing, and distant entry safety testing.


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