The Homeland Security Department's customs enforcement division has gone on a Web site shutdown spree, closing down at least 76 domains this week, according to online reports.

While many of the web domains were sites that trafficked in counterfeit brand name goods, and some others linked to copyright-infringing file-sharing materials, at least one site was a Google-like search engine, causing alarm among web freedom advocates who worry the move steps over the line into censorship.