This solution applies to all Barracuda Web Filters.
Some customers using CITRIX terminal services configured with virtual IP (VIP) addresses experience difficulty working with the Barracuda Web Filter if AVG anti-virus software is installed on the CITRIX server.
A recent update to AVG creates a proxy service on localhost of the CITRIX server and modifies the web browser settings to direct web traffic to the local AVG proxy. You will be able to determine whether this is occurring on the CITRIX server by viewing the output of TCPView or similar network diagnostic software. The web browser will appear to make connections from the VIP to 127.0.0.1.
To resolve this issue, if you install AVG 9.0 on a Citrix system using VIP and disable the link scanner and resident shield VIPs will pass. You can add the AVG process to the VIP list of configured applications.
In general, Barracuda Networks recommends using NTLM or Kerberos to authenticate CITRIX users rather than VIPs.
Link to this page: