predictable threat of terrorism. u.s. bases generally have not been at this level since the tenth anniversary of the 9/11 attacks. u.s. law enforcement is particularly concerned about isis' aggressive and successful online propaganda campaign. thousands of people in the u.s. have shown interest in isis online and u.s. officials fear some of them could be inspired to carry out attacks here. >> it really is an expansion of how the internet has been used for several years now, both in recruitment and radicalization of young people to join terrorist groups. >> reporter: now the man believed to have been in touch with one of the texas shooters is back online encouraging new supporters. after having previous twitter accounts suspended. the british-born isis recruiter junaid hussein posted his contact information on twitter for anyone who wants to "bake a cake," a well-known code phrase for building bombs. >> groups like isil or al qaeda now are calling publicly for