This is the README.kerberos file to have squid negotiate/authenticate via kerberos any addons are very welcome comments could be posted to 1) you need to add a "USER" inside your "Domain-Computers" Container called "squid". Yes a "USER" and not a Computer. You may use another name, but why ? 2) After having successfully created the user, you need to create a keytab file on your WIN box. Example: !! This is all in one line !! ktpass -princ HTTP/squid@DOMAIN.REALM -pType KRB5_NT_PRINCIPAL \ -mapuser squid -pass * -out HTTP.keytab 3) copy over HTTP.keytab to /etc/squid/ on your linux box 4) you have to tell your browsers to negotiate via kerberos Have a look at: a) Internet Explorer does not support Kerberos authentication with proxy servers http://support.microsoft.com/?scid=kb%3Ben-us%3B321728&x=19&y=14 This limitation was removed in Windows Internet Explorer 7. If Integrated Windows Authentication is turned on in Internet Explorer for Windows 2000 and Windows XP, you can complete Kerberos authentication with Web servers either directly or through a proxy server. However, Internet Explorer cannot use Kerberos to authenticate with the proxy server itself. b) Unable to negotiate Kerberos authentication after upgrading to Internet Explorer 6 http://support.microsoft.com/kb/299838/EN-US/ To resolve this issue, enable Internet Explorer 6 to respond to a negotiate challenge and perform Kerberos authentication: 1. In Internet Explorer, click Internet Options on the Tools menu. 2. Click the Advanced tab, click to select the Enable Integrated Windows Authentication (requires restart) check box in the Security section, and then click OK. 3. Restart Internet Explorer. Administrators can enable Integrated Windows Authentication by setting the EnableNegotiate DWORD value to 1 in the following registry key: HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Internet Settings Note Internet Explorer 6, when used with Microsoft Windows 98, Microsoft Windows 98 Second Edition, Microsoft Windows Millennium Edition, and Microsoft Windows NT 4.0 does not respond to a negotiate challenge and default to NTLM (or Windows NT Challenge/Response) authentication even if the Enable Integrated Windows Authentication (requires restart) check box is selected because Kerberos authentication is not available on these operating systems.