This message is simply to be used for searching in the future as I have found many people asking this question and not getting a concise answer back. This is my contribution to the problem.
Environment: squid-2.5.STABLE5-4 samba-3.0.7 Squid is configured to use NTLM authenication for all outbound http connections to the Internet. squid.conf contains the following: auth_param ntlm program /usr/bin/ntlm_auth --helper-protocol=squid-2.5-ntlmssp auth_param ntlm children 30 auth_param ntlm max_challenge_reuses 0 auth_param ntlm max_challenge_lifetime 2 minutes auth_param basic program /usr/bin/ntlm_auth --helper-protocol=squid-2.5-basic auth_param basic children 15 auth_param basic realm Some Domain Name auth_param basic credentialsttl 2 hours Problem: If Squid is configured to use auth_param ntlm only (so auth_param basic lines are not present or commented out, unlike the above example), sites that use java applets such as http://javatester.org/version.html, will error out with a java.io.IOException in the java console. This seems to apply to older (pre 1.4 ??) versions of java. We ran into the problem using Oracle's JInitiator Control Panel 1.1.8.16. Solution: Ensure you have the following in your squid.conf auth_param basic program /usr/bin/ntlm_auth --helper-protocol=squid-2.5-basic auth_param basic children 15 auth_param basic realm Some Domain Name auth_param basic credentialsttl 2 hours This will then prompt the user for username and password. Please feel free to add comments to this but in attempting to troubleshoot this particular problem, I found several people asking the questions and no answers were given.
