The effort comes as researchers are seeing terrorists increasingly use the Internet to plan bombings, recruit members and spread propaganda. "Blogging and message boards have played a substantial role in allowing communication among those who would do the United States harm," the department said in a recent notice.

Homeland Security officials are looking for companies to search the Internet for postings "in near to real-time which precede" an attack, particularly a bombing. Bombings are "of great concern" because terrorists can easily get materials and make an improvised-explosive device (IED), the department said.