IIS Security Best Practices: How to Secure Your IIS Server | Acunetix

IIS Security Best Practices: How to Secure Your IIS Server

This article was originally published by LOGON’s partner Acunetix. Click here to view the original article.

Microsoft IIS remains a core component in many enterprise environments, especially where Windows Server, Active Directory, and ASP.NET are in use. Yet IIS is often overlooked as an attack surface.

Common IIS misconfigurations attackers exploit:

Issue	Risk
Directory listing	Exposes file structures and log files
Server header disclosure	Reveals IIS version information
Weak SSL/TLS	Allows downgrade or interception attacks
Unnecessary HTTP methods	Expands attack surface
Legacy features (WebDAV, FTP)	Enables file uploads and modification
Tilde enumeration	Discovers hidden files and directories

IIS-specific attack techniques to know:

Tilde enumeration – Exploits short filename handling to reveal files not exposed through normal navigation
WebDAV abuse – Combined with weak authentication and write permissions, allows file uploads or modification
web.config exposure – Misconfigured request filtering can expose connection strings and authentication settings

IIS security checklist:

Category	Actions
Exposure Controls	Disable directory listing, remove default pages, hide IIS version headers
Access & Authentication	Apply least-privilege NTFS permissions, secure web.config, configure authentication properly
Protocol & Transport	Disable unnecessary HTTP methods, enforce TLS 1.2+
Features & Services	Disable WebDAV and FTP unless required
Monitoring	Configure IIS logging, monitor anomalies
ASP.NET Hardening	Protect VIEWSTATE, secure machine keys, disable debugging in production

Key takeaway: Hardening IIS establishes a baseline, but configuration drift happens as applications evolve. Continuous validation through automated scanning ensures your IIS server remains secure over time.

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