Ntlm authentication what is

How does ntlm authentication work? NTLM is a collection of authentication protocols created by Microsoft. Initially a proprietary protocol, NTLM later became available for use on systems that did not use Windows.

Most networks attempt to deny access to unauthorized users, which requires implementation of an authentication process. The protocol requires a client to be authenticated by providing a username and a corresponding password. To do so, the client and host go through several steps:. To keep a password sent over a network from being read by unauthorized third parties, a hash function is used in which the password is converted into an incomprehensible string of numbers with the help of a mathematical function.

Since this conversion cannot be undone very easily, hash functions play a very important role in cryptology. Information is partially relayed in the form of NTLM flags during the exchange between a client and a host. These are codes with a length of 4 bytes. Negotiation flags , which sometimes only differ from each other by one byte, provide information on the status of the sign-in process.

Windows uses NTLM as a single sign-on process SSO ; users only have to log in once to then have access to various applications within the domain. This newer authentication protocol is more secure.

However, NTLM is still in use, especially to support older services. Legacy NTLM authentication. Although it performs reliably as documented in this section, it is highly recommended that the Integrated Windows Authentication mode be used instead. It provides more robust and secure support for NTLM. When the Legacy NTLM option is enabled, the proxy challenges users who request content for proof of their credentials. The proxy then sends the proof of the user's credentials directly to the Windows domain controller to be validated.

If the credentials are valid, the proxy serves the requested content and stores the credentials in the NTLM cache for future use. When generating a web script you can preset the user name and password by enabling the option Server or Proxy Authentication Required in Web Generation Options.

This topic was last updated on May 19, , at PM. If the user selects a weak or common password, they are especially susceptible to such tactics. The name is derived from the Greek mythological character Kerberos, the three-headed dog who guards the underworld. However, NTLM is still maintained in all Windows systems for compatibility purposes between older clients and servers. NTLM is also used to authenticate local logons with non-domain controllers.

NTLM is considered an outdated protocol. As such, its benefits — when compared to a more modern solution, such as Kerberos — are limited. Yet the original promise of NTLM remains true: Clients use password hashing to avoid sending unprotected passwords over the network.

For organizations still relying on NTLM for compatibility reasons, CrowdStrike offers the following recommendations to enhance security and minimize risk. This process consists of three messages: Negotiation message from the client Challenge message from the server Authentication message from the client NTLM Authentication Process NTLM authentication typically follows the following step-by-step process: The user shares their username, password and domain name with the client.

The client develops a scrambled version of the password — or hash — and deletes the full password. The client passes a plain text version of the username to the relevant server. The server replies to the client with a challenge, which is a byte random number. The server then sends the challenge, response and username to the domain controller DC. The DC then compares the encrypted challenge and client response.