Table 1: Comparison of IIS 7.0 Authentication Methods
	Basic Authentication	Digest Authentication	NTLM	Kerberos	Client Certificate–based (SSL/TLS)	Forms Authentication
Protocol based on open standard?	Yes	Yes	No	Yes	Yes	No
Relies on Windows accounts?	Yes	Yes	Yes	Yes	No	No
Requires AD accounts?	No	Yes	Yes	Yes	No	No
Supports non-IE browsers?	Yes	Yes	No	No	Yes	Yes
Requires SSL?	Yes	No	No	No	Yes	Yes
IE version requirements	All IE versions	IE 5.0 or later	IE 2.0 or later	IE 5.0 or later	All IE versions	All IE versions
Supports authentication through firewalls and proxies?	Yes	Yes	Only on selected proxies; also works with tunnel connection	Only if Kerberos traffic is allowed; also works with tunnel connection	Yes	Yes
Overall security quality?	Weak: Base64 encoded, requires SSL	Strong: Based on a challenge-response mechanism; advanced digest authentication (default for IIS 7.0) is the recommended version	Strong: Based on a challenge-response mechanism; NTLM v2 is the recommended version	Strong: Based on an open standard	Strong: Based on asymmetric cryptographic mechanism	Strong: If combined with SSL