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Re: NTLM HTTP Authentication is insecure by design - a new writeup by Amit Klein
Date: Tue, 19 Jul 2005 13:35:36 +0400

Dear Amit Klein (AKsecurity),

--Monday, July 18, 2005, 9:40:32 PM, you wrote to bugtraq () securityfocus com:

AKA>                      NTLM HTTP Authentication
AKA>               (and possibly other connection-oriented
AKA>           HTTP authentication and authorization protocols)
AKA>                       is insecure by design

 NTLM  authentication is insecure by design for external authentication,
 because  of  "single  signon" ideology. NTLM authentication can be used
 for  NTLM  proxy  attack. For example, attacker who can hijack or spoof
 server  connection  with NTLM authentication can use this connection to
 access  different  Web server, mail server or file server with client's
 credentials.  This  is  known for many years and was discussed for many
 times.  Few  years  ago  Internet  Explorer  was  patched  to  use NTLM
 authentication  only  for  local  network zone. Local network are hosts
 with  NetBIOS name (for example WEBSRV, excluded by default from proxy)
 and list of proxy exclusions.

 So,  under default configuration, NTLM will not be used through proxy
 server, at least in Internet Explorer.


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