this add-on will install bind which is a DNS service , and so you nas will act as a DNS but will forward all the requests to OpenDNS. So you will be able to filter web access. AND IT's FREE !! OpenDNS is the leading provider of free security and infrastructure services that make the Internet safer through integrated Web content filtering, anti-phishing and DNS. OpenDNS services enable consumers and network administrators to secure their networks from online threats, reduce costs and enforce Internet-use policies. OpenDNS is used today by millions of users and organizations around the world.