FCC Plans Filtering for 2155 MHz Spectrum

Facing heavy pressure from Congress, the FCC last week delayed its planned auction for the 2155-2188 MHz band of spectrum. Among the points of contention, the auction as it is currently designed would require that the winner filter pornography from the freely-available portions of its network. I've already blogged about whether such a requirement is legally possible. Here I'll briefly touch on whether such a requirement is technically feasible.

Were filtering requirement to remain in the auction rules, the easiest way for the spectrum winner to filter pornography would be through what is known as TCP/IP header filtering. In this method, the network operator's routers would block any traffic headed to specific IP addresses (e.g. those of porn sites). But there are three problems (pdf) with this sort of method. First, IP addresses often direct to more than one website or service (e.g. email). Therefore users would not be able to access some websites or services because they shared an IP address with a blocked site. Second, no network operator could track every pornographic site, and so the TCP/IP filter would almost certainly fail to capture a significant portion of online pornography. Finally, any filter that identifies sites by keywords would block some sites that were not pornographic in nature. Sites about sexually transmitted infections, safe-sex, or any number of other topics might be blocked that ought not to be.

Ultimately, filtering might not be necessary to protect children from pornography. Depending who wins the auction, consumers might have to pay as much as $150 for the hardware to get on the network, keeping access unaffordable for most children.