All Barracuda Web Filters, firmware versions 3.0 and above.
A user could be trying to proxy through the Barracuda Web Filter using port 80 instead of port 8080. The Barracuda Web Filter hosts the proxy service on port 8080 (by default). Please make sure that your users are proxying to the Barracuda Web Filter through port 8080, rather than port 80.
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