The "basic" authentication scheme, the simplest method of authentication and one of the most commonly used authentication method sends authentication details in clear.
Digest authentication, never sent across the network user's credentials in the clear, but transmits as an MD5 digest of the user 's credentials.
NTLM, a Microsoft-proprietary protocol authenticates users and computers based on an authentication challenge and response.
Certificated authentication which uses public key cryptography and digital certificate to authenticate is stronger than other authentication mechanisms.
Forms based Authentication is a system in which unauthenticated requests are redirected to a web form where the unauthenticated users are required to provide their credentials.
Attackers make use of different tools to get better of the authentication protocols.
It is therefore necessary to evaluate and implement the most secure option while designing web applications to counter cracking activities.