All Barracuda Web Filters, firmware versions 3.3.03 and above.
When first enabling HTTPS filtering, any client PCs that had previously established an HTTPS session will not be blocked. In this situation, the HTTPS website's IP address remains in the user's local DNS cache (as well as in the DNS table on the core router or domain controller) until the DNS request time-to-live (TTL) expires. This can take up to a day or two, depending upon how the HTTPS sites configure TTL. What this means is that until the user performs another DNS lookup of a website's domain name, the Barracuda Web Filter won't automatically know which domain is associated with the IP address and won't be able to perform any domain blocks on those connections.
To hurry this along, you can manually clear the DNS cache on your network's DNS servers.
For more information on the Barracuda Web Filter and HTTPS filtering, see Solution #00003316.
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