As schools struggle with shrinking budgets and try to work around technology funding cuts, many are turning to OpenDNS, a free network security service that provides content filtering, anti-phishing security, and domain name system (DNS) resolution. 

DNS is a database system that translates a domain name or URL--which is how the average internet user calls up a web page--into an IP address. In essence, it takes the alphabetical name for a web site and translates it into the numerical IP address.

OpenDNS features more than 54 categories of blockable internet content, and the web sites listed in those categories are contributed largely by OpenDNS users from school districts such as Detroit, Baltimore, and San Diego.

Although entire categories may be blocked, the service allows for individual exceptions. For instance, a district might choose to block all social networking sites from its computers, but a teacher's classroom blog can be entered as a permissible site so the teacher and students can access the blog from school.

The globally distributed network service, which is a free alternative to software from companies such as Websense and Lightspeed, operates by accepting web site requests from school customers. Those requests are routed to the closest OpenDNS data center, such as the center in Chicago or Washington, D.C.

OpenDNS examines the user's IP address with each incoming web site request and brings up the corresponding school or district's web site preferences. The service matches those preferences against the web site request. If a student tries to access an approved site, OpenDNS approves the request and connects the student to the site in question. If a student tries to access a blocked web site, such as MySpace, OpenDNS verifies that MySpace is on the school's blocked list and will deny the student access to the site.

"OpenDNS is a service that runs in the cloud; every network usually has a DNS server, and all you have to do is change [a preference] in your DNS server" for the service to work, said David Ulevitch, OpenDNS founder.

For instance, a network administrator would adjust a school's DNS server so that external or "all other" DNS requests are forwarded to OpenDNS, and OpenDNS would then check web site requests against the school's preference list.

In the same way that a home internet user might have Verizon internet service but will opt for Gmail or Yahoo eMail service instead of Verizon's built-in eMail service, users can "unbundled" their DNS and opt for a service such as OpenDNS.

Roughly 25,000 schools currently use the free, ad-supported service, and network administrators can connect with each other to discuss OpenDNS and other technology issues in a recently launched K-12 community forum.

Vermont's Bennington-Rutland School District uses OpenDNS as part of its new network structure. Superintendent Daniel French said it's a simpler, easy-to-manage solution that offers content filtering but does not inhibit learning opportunities for the district's students.