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What is WAF (web application firewall)?

A system placed in front of a web application that inspects the content of HTTP requests, such as the URL, parameters and headers, and blocks requests containing patterns typical of SQL injection, cross-site scripting and similar attacks, or requests that do not fit defined rules. It targets attacks on applications that ordinary firewalls, which control traffic by IP address and port number, cannot stop. It is also used as temporary protection until a vulnerability is fixed (virtual patching), but it is not a substitute for the fix.

Japanese name: WAF(Webアプリケーションファイアウォール)

WAF (web application firewall) appears in 2 practice questions across 2 topics, including Cyber Attacks and Defense in Practice, Computer Networking Basics.

Field: Cyber Attacks and Defense in Practice

Try it: questions about WAF (web application firewall)

Which of the following correctly describes a WAF (web application firewall)?

  1. AA device that decides whether to pass or block traffic by looking only at IP addresses and port numbers, without examining the content of HTTP
  2. BWith a WAF in place, all attacks including SQL injection can be prevented completely even without fixing the web application's vulnerabilities
  3. CPlaced in front of a web application, it inspects the content of HTTP requests and blocks requests containing typical attack strings
Show answer and explanation

Answer: C. Placed in front of a web application, it inspects the content of HTTP requests and blocks requests containing typical attack strings

Ordinary firewalls control traffic by IP address, port number and so on, so they cannot stop attacks on web applications that pass through the allowed HTTPS port. A WAF inspects the content of HTTP requests, such as the URL, parameters and headers, and blocks requests with patterns typical of SQL injection or cross-site scripting, or requests that do not fit rules defined for the application. It is also used as temporary protection (virtual patching) between the discovery of a vulnerability and the completion of its fix. However, some attacks slip past the rules, so it is not a substitute for fixing the vulnerability itself.

WAF (web application firewall) in the explanations

Questions that mention WAF (web application firewall) (2)

  1. Which of the following correctly describes a WAF (web application firewall)?
  2. Which correctly describes the basic function of a (packet-filtering) firewall?

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Comparisons that include this term

Related terms

Port number HTTP (Hypertext Transfer Protocol) SQL injection Cross-site scripting (XSS) TLS Cyber Kill Chain Digital forensics EDR (endpoint detection and response) Incident response Indicator of compromise (IoC)

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