Web Application Firewall (WAF)

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A web application firewall (WAF) is a firewall designed specifically to protect software running on web servers and their back-end databases from code injection and DoS attacks.

• type of reverse proxy
• primarily validates input and output
• use application-aware processing rules to
  • filter traffic
  • perform application-specific intrusion detection
• can be programmed with signatures of known attacks
  • and use pattern matching to block requests containing suspect code
• output from a WAF will be written to a log
  • can reveal potential threats to the web application
• may be deployed as:
  • an appliance protecting the zone that the web server is placed in
  • or as plug-in software for a web server platform