SECURITY / A CONCEPT NOTE
WAF
filtering malicious traffic before it reaches your application
Overview · mechanism
pitfall · examples
01 / THE SHORT VERSION
The idea in a few sentences.
A Web Application Firewall (WAF) inspects HTTP/HTTPS traffic at the edge and blocks common attacks — SQL injection, cross-site scripting (XSS), cross-site request forgery (CSRF), and OWASP Top 10 threats. AWS WAF, Cloudflare WAF, and ModSecurity allow you to write custom rules to block or rate-limit specific patterns, IPs, or geographies.
02 / FOLLOW THE MECHANISM
How a waf blocks an attack
Attacker
sends
GET /products?search=1' OR '1'='1' --— a classic SQL injection attempt.WAF
receives the request at the edge (before it reaches your origin). It inspects headers, query strings, and body.
Rule engine
matches the payload against OWASP core rule sets — the
' OR '1'='1'pattern triggers a SQLi rule.Action
the WAF blocks the request with
403 Forbiddenand logs the event. The attacker never touches your server.
04 / COMMAND NOTES
Read the command, then the result.
Inspect the flags and arguments before trying an example. Snippets can need local setup, replacement values, or resources in your own environment.
list WAF web ACLs
aws wafv2 list-web-acls --scope REGIONALinspect WAF rules and conditions
aws wafv2 get-web-acl --name my-acl --scope REGIONAL --id ACL_ID05 / CHECK YOURSELF
Could you explain WAF to a teammate?
Try it out loud in two sentences: what it is, and the one detail that changes the picture. If you stall, the gap is the part to reread.
Up next in Security & identitymTLSmutual TLS — both sides prove their identity, not just the server