# Application Gateway WAF is Enabled in Prevention mode
Azure Application Gateway Web Application Firewall (WAF) protects web applications from common exploits and vulnerabilities, including SQL injection…
Source: https://maester.dev/docs/tests/ZTA.25541
## Overview
Azure Application Gateway Web Application Firewall (WAF) protects web applications from common exploits and vulnerabilities, including SQL injection, cross-site scripting, and other OWASP Top 10 threats. WAF operates in two modes: Detection and Prevention. Detection mode logs matched requests but doesn't block traffic, while Prevention mode actively blocks malicious requests before they reach the backend application. When WAF is in Detection mode, web applications remain exposed to exploitation even though threats are being identified.
Without WAF in Prevention mode:
- Threat actors can exploit web application vulnerabilities such as SQL injection and cross-site scripting, because matched requests are only logged, not blocked.
- Organizations lose the active protection that managed and custom WAF rules provide, which reduces WAF to an observability tool rather than a security control.
## Remediation
- [Configure WAF on Azure Application Gateway](https://learn.microsoft.com/azure/web-application-firewall/ag/ag-overview?wt.mc_id=zerotrustrecommendations_automation_content_cnl_csasci#waf-modes) to switch the WAF policy from **Detection mode** to **Prevention mode**.
- [Create and manage WAF policies for Application Gateway](https://learn.microsoft.com/azure/web-application-firewall/ag/create-waf-policy-ag?wt.mc_id=zerotrustrecommendations_automation_content_cnl_csasci) to apply Prevention mode settings across all Application Gateway instances.
## Run it
The check runs as part of the whole assessment, with the ZeroTrustAssessment module installed:
```powershell
Install-Module ZeroTrustAssessment -Scope CurrentUser
Connect-Maester
Invoke-Maester -Pack ZTA -SkipBuiltIn
```
Leave out `-SkipBuiltIn` to run Maester's own checks in the same run.
About this check
| | |
| --- | --- |
| Severity | High |
| Effort to fix | Low |
| Impact on users | Low |
| Pillar | Network |
| Category | Azure Network Security |
| Product | [Azure](/docs/tests/products/azure) |
| Feature | Network security |
| Area | Infrastructure hardening |
| ATT&CK | [T1190](/docs/tests?mitre=T1190) Exploit Public-Facing Application |
| Licence | Azure WAF, Azure Application Gateway Standard SKU |
| Tenant | Workforce |
Product, feature, area and ATT&CK are Maester's: the assessment does not record them, so Maester keeps them in the pack's `taxonomy.json`.