promote a story hundreds or thousands of times, then that puts it into trending feeds. once it's in a trending feed, it takes it on a life of its own. >> reporter: experts who research russia's fake news campaigns testified before the senate intelligence committee, explaining how putin's government uses an army of trolls, online critics who push their agendas, to confuse and frighten audiences in the west, an idea that played out dramatically on the showtime series "homeland." a troll factory where hundreds of employees toil away, posting fake news under fake names. >> iraq bob. >> that's me. >> navy wife. >> that's me too. >> reporter: their marching orders, post phony stories and tweets and spread them as widely as possible. experts say the real life troll factories used by r&bens may not look as slick as the tv version, but they are real. they say paid trolls who spread fake reports can amplify their impact using bot nets.