[Security] What is Web Application Firewall(WAF)? Top 10+ WAF 2021

What is a Web Application Firewall?

A WAF or Web Application Firewall secures web applications by sifting and observing HTTP traffic between a web application and the Internet. It regularly shields web applications from cyberattacks, for example, cross-site forgery, file inclusion, cross-site scripting (XSS), and SQL injection, among others. A Web application firewall is a layer 7 protection (as per OSI model) and isn’t intended to shield against a wide range of cyberattacks. This technique for cyberattack mitigation is generally essential for a set-up of tools that together make an all-encompassing defence against a scope of cyberattack vectors.


What is the difference between Firewall and web application firewall (WAF)?

Web Application Firewall protects web applications against malicious cyberattacks and vulnerabilities. A firewall protects only against network attacks and threats. Both firewalls and web application firewalls not only vary in the type of protection they range but also in the entire function.

  1. The main difference between WAF and firewall is that WAF sits before the servers and apps, providing defence against threats that target server machines, whereas Firewall is placed on the entry of a network, working as a boundary between known and unknown threats.
  2. Standard firewalls are predestined to permit or reject access to networks. WAF firewalls emphasis threats targeted at HTTP/HTTPS servers and applications.
  3. Firewall attention on layer 3 and layer 4 (as in OSI Model), whereas Web application firewall typically defences Layer 7 of the OSI model
  4. The firewall includes Packet-Filtering algorithms, stateful/stateless inspection algorithms, whereas WAF includes algorithms similar to Anomaly Detection algorithms, Heuristics algorithms, and Signature-based algorithms.

What is the major difference between allow list and blocklist WAFs?

Allow List – A Web application firewall based on an allow list (positive approach model) only permits traffic that has been pre-approved. This is like the security guard at an exclusive party, he or she only allows persons who are on the list.

Block List A Web application firewall based on a blocklist (negative approach model) guards against identified attacks. This is also like a security guard instructed to deny admittance to guests who don’t meet the entry criteria.

What is network-based, host-based, and cloud-based WAFs?

Network-Based Web Application Firewall –

A network-based WAF is generally hardware equipment. Since they are deployed nearby, they minimize latency, but network-based WAFs are the most expensive choice and also need the storage and maintenance of physical equipment.

Host-Based Web Application Firewall –

A host-based WAF may be entirely combined into an application’s software. This solution is more affordable than a network-based WAF and offers more adaptability. The downside of a host-based WAF is the consumption of local server resources, implementation complexity, and maintenance costs. These components typically require implementing time and maybe overpriced.

Cloud-Based Web Application Firewall –

Cloud-based WAFs is an inexpensive choice that is very easy to deploy; they typically offer a turnkey installation that is as simple as a modification in DNS to transmit traffic. Cloud-based WAFs also have a negligible upfront cost, as users pay monthly or annually for security as a service. Cloud-based WAFs can also offer a solution that is consistently updated to protect against the newest threats without any additional work or cost on the user’s end. The drawback of a cloud-based WAF is that user’s hand over the responsibility to a third-party, therefore some features of the WAF may be a black box to them. Learn about Cloudflare’s cloud-based WAF solution.

The Best Application Firewalls 2021


Akamai WAF

Price: Free Trial, Quote-based Plan.

Features: Customizable and Automated Protection, Advanced API Security, Zero-Second DoS, Mitigation SLA, Granular Attack, Visibility and Reporting, Managed Security Services.


Best: Mid to large-sized businesses.

Attacks: Advanced Application and Network Layer, Control SQL injection, Malicious file execution, Cross-site scripting DDoS attacks

Website Link: Akamai WAF



Price: Basic | Free, Advanced |14-day free trial | $99 per month, Premium| $399 per month

Features: Uncover Vulnerabilities Non-Stop. Manual Pen-Testing, Patch Vulnerabilities Immediately, Checks for False Positives, DDoS Protection


Best: Small to large enterprises

Attacks: WAF with risk detection, risk monitoring, risk protection, and website acceleration

Website Link: AppTrana



Price: Web ACL: $5.00 per month (prorated hourly), Rule: $1.00 per month (prorated hourly), Request: $0.60 per 1 million requests.

Features: Agile protection against web attacks, Improved web traffic visibility, Ease of deployment and maintenance, Cost-effective web application protection, Security integrated with how you develop applications


Best: Scalable use for businesses of all sizes as long as they are AWS clients.

Attacks: Cross-Site Scripting (XSS), SQL injections, DDoS attacks.

Website Link: AWS WAF


Barracuda WAF

Price: Free trial, Quote based pricing

Features: Complete OWASP Protection, Advanced Bot Protection, Application Learning (Adaptive Profiling), Virtual Patching and Vulnerability Scanner Integration, Malware Protection and Anti-Virus


Best: Small to mid-sized enterprises.

Attacks: API security, bot mitigation, alerting, and reporting.

Website Link: Barracuda WAF


Citrix WAF

Price: Free Demo, Quote-based pricing

Features: Ensures PCI DSS compliance. Protects web apps from known and emerging threats, infrastructure-layer security, load balancing, DDoS defence, and content inspection.


Best: Mid to large-sized businesses – the best WAF tool for existing Citrix clients.

Attacks: deep-packet inspection of web protocols such as HTTPS, HTTP, and XML.

Website Link:: Citrix WAF


Cloudflare WAF

Price: Free: $0 per month, Pro: $20 per month, Business: $200 per month, Enterprise: Ask for Quote.

Features: Logging and Reporting, Issue Tracking, Security Monitoring, Reporting and Analytics, Application-Layer Control.


Best: Personal usage, small to mid-sized businesses, as well as high-level enterprises.

Attacks blocks from Blocks OWASP Top 10, Limits comment spam, protects key ports (SSH, telnet, FTP), DDoS attacks, SQL injections, Blocks threats based on reputation, blacklists, HTTP headers, and more

Website Link: Cloudflare WAF


F5 Advanced WAF

Price: Cloud-based Service Subscriptions, On-Premise Software

Features: Advanced application protection, Proactive bot defence, Behavioural DoS, Defences for the OWASP Top 10, Stolen Credential Protection


Best: Mid to large-sized enterprises.

Website Link: F5 Advanced WAF


Fortinet FortiWeb

Price: Free Demo, Quote-based pricing

Features: Detailed analysis of attack sources through visual reporting tools, False Positive Mitigation Tools, Correlated threat detection with Al-based behavioural scanning, Fortinet Security Fabric integration, Visual analytics tools for advanced threat insights.


Best: Mid to large-sized businesses.

Attacks: defends from cyberattacks and known vulnerabilities.

Website Link: Fortinet FortiWeb


Imperva WAF

Price: Free tools for Data Classification and Database Vulnerability Testing, Plus | Quote-based, Premium | Quote-based

Features: Secure cloud and on-prem apps, Stop OWASP Top 10 and Automated Top 20, Attack detection, SIEM integration, Extensive reporting


Best: Small to large-sized enterprises.

Website Link: Imperva WAF



Price: SecureAlert | $149.99 per site per year, SecureStarter | $299.99 per site per year, SecureSpeed | $499.99 per site per year, Custom Solutions | Contact vendor for quotes

Features: Protection Against Top Ten Online Threats, Data Protection, Prevent Common Hacks, Block Backdoor Access, Protect Published Content


Best: Small to mid-sized businesses.

Attacks: spammers

Website Link: SiteLock


Sucuri Website Firewall

Price: Basic: $9.99 per month, Pro: $19.98 per month, Business: $499.99 per year.

Features: Uncover Vulnerabilities, Non-Stop Manual Pen-Testing, Patch Vulnerabilities Immediately, Checks for False Positives, DDoS Protection.


Best: Small to large enterprises.

Attacks: Cross-Site Scripting (XSS), Hidden field manipulation, Cookie poisoning, Layer 7 DoS attacks, Parameter tampering, SQL injections, Blocks OWASP Top 10.

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