I need for Ruby on Rail application set authentication via Active Directory using Kerberos authentication. Some technical information: I are using Apache installed mod_auth_kerb In httpd.conf I added LoadModule auth_kerb_module modules/mod_auth_kerb.so In /etc/krb5.conf I added following configuration [logging] default = FILE:/var/log/krb5libs.log kdc = FILE:/var/log/krb5kdc.log admin_server = FILE:/var/log/kadmind.log [libdefaults] default_realm = EU.ORG.COM dns_lookup_realm = false dns_lookup_kdc = false ticket_lifetime = 24h forwardable = yes [realms] EU.ORG.COM = { kdc = eudc05.eu.org.com:88 admin_server = eudc05.eu.org.com:749 default_domain = eu.org.com } [domain_realm] .eu.org.com = EU.ORG.COM eu.org.com = EU.ORG.COM [appdefaults] pam = { debug = true ticket_lifetime = 36000 renew_lifetime = 36000 forwardable = true krb4_convert = false } When I test kinit validuser and enter password then authentication is successful. klist returns: Ticket cache: FILE:/tmp/krb5cc_600 Default principal: [email protected] Valid starting Expires Service principal 02/08/13 13:46:40 02/08/13 23:46:47 krbtgt/[email protected] renew until 02/09/13 13:46:40 Kerberos 4 ticket cache: /tmp/tkt600 klist: You have no tickets cached In application Apache configuration I added IfModule mod_auth_kerb.c> Location /winlogin> AuthType Kerberos AuthName "Kerberos Loginsss" KrbMethodNegotiate off KrbAuthoritative on KrbVerifyKDC off KrbAuthRealms EU.ORG.COM Krb5Keytab /home/crmdata/httpd/apache.keytab KrbSaveCredentials off Require valid-user </Location> </IfModule> I restarted apache Now some tests: When I try to access application from Win7, I got pop-up message box, with text: Warning: This server is requesting that your username and password be sent in an insecure manner (basic authentification without a secure connection) When I enter valid credentials then my application opens successfully, and all works fine. Questions: Is ok that for user pop-ups such windows? If I use NTLM authentication then there no such pop-up. I checked IE Internet Options and there 'Enable Integrated Windows Authentication' is checked. Why IE try to send username and password to application apache? If I correct to understand then Windows self must make authentication via Active Directory using Kerberos protocol. When I try to access application from Win7 and I enter incorrect credentials to pop-up message box Application say Authentication failed (this is OK) In apache error log I see: [error] [client 192.168.56.1] krb5_get_init_creds_password() failed: Client not found in Kerberos database But now I cannot get possibility to enter valid credentials, only when I restart IE I can get again pop-up box. What could be incorrect or missing in my Kerberos setup? I read in some blog post that probably something is needed to be done in Active Directory side. What exactly?