An anonymous reader writes "T-Mobile USA offers a 'feature' to restrict access to certain kinds of content. This is called Web Guard. Supposedly Web Guard is supposed to inhibit access to content that falls under certain categories. The Open Observatory of Network Interference (OONI), developed a tool to detect what sites were being censored. Amongst them were political news sites, foreign sports news sites and other sites that should not have been censored." It's quite an eclectic bunch of sites that are blocked, but then censorware tends to break in interesting ways, even when it's not by design.