Editor’s Note:  The following was written by guest columnist, Sam Beskur, CTO of Global Gossip.  APconnections and Global Gossip have partnered to offer a  joint hotel service solution, HMSIO.  Read our HMSIO service offering datasheet to learn more.

Traffic Filtering with OpenDNS

Abstract

AUP (Acceptable Use Policy) violations which include DMCA infringements on illegal downloads (P2P, Usenet or otherwise) have been hugely troublesome in many locations where we provide public access WiFi.  Nearly all major carriers here in the US now have some form of notification system to alert customers when violation occur and the once that don’t send notifications are silently tracking this behavior.

As a managed service provider it is incredibly frustrating to receive these violation notifications as they never contain information one needs to stop the abuse but only the WAN IP of the offending location.  An end user who committed the infraction is often behind a NATed private address (192.168.x.x or 172.x.x.x) and for reasons still unknown to me they never provide information on the site hosting the illegal material, botnet, adware etc.

When a customer, on whose behalf one may be providing managed services for, receives one of these notifications this can jeopardize your account.

Expensive layer 7 DPI appliances will do the job in filtering P2P traffic but often times customers are reluctant to invest in these devices for a number of reasons: yet another appliance device to power, configure, maintain, support, another point of failure, another config to backup, no more Rackspace, etc, etc ad nausea.

Summary

Below we outline an approach that uses a cloud approach based on OpenDNS and NetEq which has very nearly eliminated all AUP violations across the networks we manage.

Anyone can use the public OpenDNS servers at the following addresses:

208.67.222.222

208.67.220.220

If however, one wishes to use the advanced filter capabilities you will need to subscribe to and create a paid account and register the static WAN IP of the address you are trying to filter.  Prices vary.

1. Adjusted our content filter/traffic shaper (NetEqualizer) to limit/block # P2P connections.

2. Configure your router / gateway device / dhcp server to use 208.67.222.220,  208.67.222.222  as primary and secondary DNS server.

    

3. Once you have an OpenDNS account add your location for filtering and configure DNS blocking of P2P and malware sites         

4. In order to prevent the more technically savvy end users from specifying ones own DNS server (8.8.8.8, 4.2.2.2, 4.2.2.1, etc.) it is a VERY good idea to configure your gateway to block all traffic on port 53 to all endpoints accept the OpenDNS servers.  DNS uses UDP port 53 so configuring this within IPTables (maybe even another feature for NetEqualizer) or within Cisco IOS is fairly trivial.  If you’re router doesn’t allow this hack it or get another one.

    

Depending on your setup there are a number of other techniques that can be added to this approach to further augment your ability to track NATed end user traffic but as I mentioned these steps alone have very nearly eliminated our AUP violation notifications.