Hi, in short : Every time a user click on a link in a MS Office document or select some Internet related app (like MS Windows Media Player), the user if forced to re-authenticate (a popup window appears). We have tested using Firefox instead IE7/IE8 and happens the same, but, if we use OpenOffice.org and Firefox in the same machines, no re-authentication is required. So, it seems this is a MS related problem with Squid. (Time and resource usage related stuff has been tested and are not the source of this problem). The authentication uses the basic one (not NTLM) and goes to an Active Directory. Any clue about it will help us a lot! Thanks in advance. PD: Some extract from access.log : 127.0.0.1 - smedina [30/Sep/2009:16:40:39 -0500] "GET http://ads1.msn.com/library/dap.js HTTP/1.0" 304 375 TCP_IMS_HIT:NONE 127.0.0.1 - smedina [30/Sep/2009:16:40:39 -0500] "GET http://rad.msn.com/ADSAdClient31.dll? HTTP/1.0" 403 1522 TCP_DENIED:NONE 127.0.0.1 - smedina [30/Sep/2009:16:40:40 -0500] "GET http://c.microsoft.com/trans_pixel.asp? HTTP/1.0" 200 593 TCP_MISS:DIRECT 127.0.0.1 - smedina [30/Sep/2009:16:40:40 -0500] "GET http://m.webtrends.com/dcs8kzhcc00000ww68ffquzt0_6o5q/dcs.gif? HTTP/1.0" 200 716 TCP_MISS:DIRECT 127.0.0.1 - smedina [30/Sep/2009:16:40:40 -0500] "GET http://js.microsoft.com/library/svy/broker-config.js? HTTP/1.0" 200 2766 TCP_MISS:DIRECT 127.0.0.1 - smedina [30/Sep/2009:16:40:40 -0500] "GET http://m.webtrends.com/dcs8kzhcc00000ww68ffquzt0_6o5q/dcs.gif? HTTP/1.0" 200 716 TCP_MISS:DIRECT 127.0.0.1 - smedina [30/Sep/2009:16:40:42 -0500] "GET http://go.microsoft.com/fwlink/? HTTP/1.0" 302 659 TCP_MISS:DIRECT 127.0.0.1 - smedina [30/Sep/2009:16:40:43 -0500] "GET http://catalog.update.microsoft.com/ HTTP/1.0" 302 565 TCP_MISS:DIRECT 127.0.0.1 - smedina [30/Sep/2009:16:40:43 -0500] "GET http://catalog.update.microsoft.com/v7/site HTTP/1.0" 301 575 TCP_MISS:DIRECT 127.0.0.1 - smedina [30/Sep/2009:16:40:43 -0500] "GET http://catalog.update.microsoft.com/v7/site/ HTTP/1.0" 200 15257 TCP_MISS:DIRECT 127.0.0.1 - smedina [30/Sep/2009:16:40:43 -0500] "GET http://catalog.update.microsoft.com/v7/site/Style/catalog.css HTTP/1.0" 304 316 TCP_IMS_HIT:NONE 127.0.0.1 - smedina [30/Sep/2009:16:40:44 -0500] "GET http://catalog.update.microsoft.com/v7/site/Script/CommonTypes.js? HTTP/1.0" 304 397 TCP_MISS:DIRECT 127.0.0.1 - smedina [30/Sep/2009:16:40:44 -0500] "GET http://catalog.update.microsoft.com/v7/site/SiteConstants.aspx? HTTP/1.0" 200 13094 TCP_MISS:DIRECT 127.0.0.1 - smedina [30/Sep/2009:16:40:44 -0500] "GET http://catalog.update.microsoft.com/v7/site/ClientControl/en/x86/MuCatalogWebControl.cab? HTTP/1.0" 200 1609 TCP_MISS:DIRECT 127.0.0.1 - smedina [30/Sep/2009:16:40:45 -0500] "GET http://catalog.update.microsoft.com/v7/site/Install.aspx HTTP/1.0" 200 18118 TCP_MISS:DIRECT 127.0.0.1 - smedina [30/Sep/2009:16:40:45 -0500] "GET http://catalog.update.microsoft.com/v7/site/SiteConstants.aspx? HTTP/1.0" 200 13094 TCP_MISS:DIRECT 127.0.0.1 - smedina [30/Sep/2009:16:40:45 -0500] "GET http://catalog.update.microsoft.com/v7/site/Script/MasterComponents.js? HTTP/1.0" 304 397 TCP_MISS:DIRECT 127.0.0.1 - smedina [30/Sep/2009:16:40:45 -0500] "GET http://catalog.update.microsoft.com/v7/site/Images/decor_BigUpArrow_head.gif HTTP/1.0" 304 317 TCP_IMS_HIT:NONE 127.0.0.1 - smedina [30/Sep/2009:16:40:45 -0500] "GET http://catalog.update.microsoft.com/v7/site/Images/decor_BigUpArrow_trunk.gif HTTP/1.0" 304 317 TCP_IMS_HIT:NONE 127.0.0.1 - smedina [30/Sep/2009:16:40:45 -0500] "GET http://catalog.update.microsoft.com/v7/site/Images/decor_BigUpArrow_stem.gif HTTP/1.0" 304 317 TCP_IMS_HIT:NONE 127.0.0.1 - smedina [30/Sep/2009:16:40:45 -0500] "GET http://catalog.update.microsoft.com/v7/site/Images/spacer.gif HTTP/1.0" 304 317 TCP_IMS_HIT:NONE 127.0.0.1 - smedina [30/Sep/2009:16:40:45 -0500] "GET http://catalog.update.microsoft.com/v7/site/Images/bg_YellowGradient.gif HTTP/1.0" 304 317 TCP_IMS_HIT:NONE 127.0.0.1 - smedina [30/Sep/2009:16:40:45 -0500] "GET http://catalog.update.microsoft.com/v7/site/Images/bg_BigGlobe.jpg HTTP/1.0" 304 318 TCP_IMS_HIT:NONE 127.0.0.1 - smedina [30/Sep/2009:16:40:46 -0500] "GET http://catalog.update.microsoft.com/v7/site/ClientControl/en/x86/MuCatalogWebControl.cab? HTTP/1.0" 200 72747 TCP_MISS:DIRECT 127.0.0.1 - - [30/Sep/2009:16:40:46 -0500] "GET http://crl.microsoft.com/pki/crl/products/CodeSignPCA2.crl HTTP/1.0" 407 2039 TCP_DENIED:NONE 127.0.0.1 - smedina [30/Sep/2009:16:40:51 -0500] "GET http://catalog.update.microsoft.com/v7/site/Install.aspx HTTP/1.0" 200 18118 TCP_MISS:DIRECT 127.0.0.1 - smedina [30/Sep/2009:16:40:51 -0500] "GET http://catalog.update.microsoft.com/v7/site/Style/catalog.css HTTP/1.0" 304 316 TCP_IMS_HIT:NONE 127.0.0.1 - smedina [30/Sep/2009:16:40:51 -0500] "GET http://catalog.update.microsoft.com/v7/Site/WebResource.axd? HTTP/1.0" 304 439 TCP_MISS:DIRECT 127.0.0.1 - smedina [30/Sep/2009:16:40:51 -0500] "GET http://catalog.update.microsoft.com/v7/Site/ScriptResource.axd? HTTP/1.0" 304 439 TCP_MISS:DIRECT 127.0.0.1 - smedina [30/Sep/2009:16:40:52 -0500] "GET http://catalog.update.microsoft.com/v7/site/Script/CommonTypes.js? HTTP/1.0" 304 397 TCP_MISS:DIRECT 127.0.0.1 - smedina [30/Sep/2009:16:40:52 -0500] "GET http://catalog.update.microsoft.com/v7/site/Script/MasterComponents.js? HTTP/1.0" 304 396 TCP_MISS:DIRECT 127.0.0.1 - smedina [30/Sep/2009:16:40:52 -0500] "GET http://catalog.update.microsoft.com/v7/Site/ScriptResource.axd? HTTP/1.0" 200 23939 TCP_MISS:DIRECT 127.0.0.1 - smedina [30/Sep/2009:16:40:52 -0500] "GET http://catalog.update.microsoft.com/v7/site/SiteConstants.aspx? HTTP/1.0" 200 13094 TCP_MISS:DIRECT 127.0.0.1 - smedina [30/Sep/2009:16:40:52 -0500] "GET http://catalog.update.microsoft.com/v7/site/Images/decor_BigUpArrow_head.gif HTTP/1.0" 304 317 TCP_IMS_HIT:NONE 127.0.0.1 - smedina [30/Sep/2009:16:40:52 -0500] "GET http://catalog.update.microsoft.com/v7/site/Images/decor_BigUpArrow_stem.gif HTTP/1.0" 304 317 TCP_IMS_HIT:NONE 127.0.0.1 - smedina [30/Sep/2009:16:40:52 -0500] "GET http://catalog.update.microsoft.com/v7/site/Images/spacer.gif HTTP/1.0" 304 317 TCP_IMS_HIT:NONE 127.0.0.1 - smedina [30/Sep/2009:16:40:52 -0500] "GET http://catalog.update.microsoft.com/v7/site/Images/decor_BigUpArrow_trunk.gif HTTP/1.0" 304 317 TCP_IMS_HIT:NONE 127.0.0.1 - smedina [30/Sep/2009:16:40:53 -0500] "GET http://catalog.update.microsoft.com/v7/site/Images/bg_BigGlobe.jpg HTTP/1.0" 304 318 TCP_IMS_HIT:NONE 127.0.0.1 - smedina [30/Sep/2009:16:40:53 -0500] "GET http://catalog.update.microsoft.com/v7/site/Images/bg_YellowGradient.gif HTTP/1.0" 304 317 TCP_IMS_HIT:NONE 127.0.0.1 - smedina [30/Sep/2009:16:40:54 -0500] "GET http://catalog.update.microsoft.com/v7/site/ClientControl/en/x86/MuCatalogWebControl.cab? HTTP/1.0" 200 72747 TCP_MISS:DIRECT --- Walter Cuestas Agramonte, Certified | Ethical Hacker (C|EH) SANS/GIAC Certified Penetration Tester (GPEN) Gerente General Phone : 511-997926168 Ethical Hacking/Forensics/InfoSec http://www.open-sec.com http://ehopen-sec.blogspot.com/