We’ve just updated the firmware on our NSA 4500 to 18.104.22.168-3o and have started playing with the Application Firewall and DPISSL (Deep Packet Inspection). The 4500 is a Layer 7 firewall and the application firewall feature lets you do some pretty tricky filtering. We’ve noticed that some of the student machines coming in for repair have bittorrent clients installed. At the moment that sort of traffic is blocked by our ISA firewall/proxy which is the gateway for the Student Netbook VLAN, but we want to remove that over the next few months because it causes a bottleneck for heavy traffic, like heavy ClickView use. When we remove ISA we can either use the Sonicwall or ACL rules on the ProCurve 5400 (or both) to filter the traffic between the netbooks and the rest of the world. After the firmware update with the addition of the DPISSL it seemed like a good chance to see how good the filtering was on the NSA4500.
Before creating the new application firewall policy, I had to create an object for the bittorrent traffic. The Sonicwall has an IDP category for all P2P traffic which has signatures for many P2P applications. You can block traffic for particular applications, eg only block Azureus and allow other bittorrent clients
With the Application object defined, we can create the policy. In this case we wanted to stop all bittorrent traffic, however, its possible to excluded addresses and or users, which would be handy with the SSO. The rule will look for any traffic deemed to be P2P going through the sonicwall and will drop the packets. nice and easy
Any requests that match the rule are blocked and can be checked in the log view, which can be filtered by application firewall
Setting up uTorrent on a test machine and queuing up some files showed that the rule was working properly and not allowing any traffic to get through. The sonicwall not only blocked the file transfer but also the attempts to look for other peers etc
The combination of the application firewall and the DPISSL would also prevent this traffic from running over secure ports or ssl vpn type setups.
Application firewall rules can also be configured to shape traffic to/from any site on the web. At the moment we’ve configured a rule to shape traffic to megaupload and other download sites that work over port 80, and depending on Facebook traffic that could be a contender too. Another type of rule that was described in some sonicwall promotional guff was a rule to catch IE6 traffic and redirect it to a warning page to upgrade your version of IE. That rule sounds like a good idea, I think that might be my next one