The charges range from providing material support to terrorists to weapons possession to conspiracy. Most of those charged are US citizens. And 16 were stopped at the airport with a ticket in their pockets with apparent plans to join the Islamic State. Arrests nationwide of Americans on ISIS-related charges are growing, and FBI Director James Comey said the threat from the terror organization has become a bigger menace to the United States than al-Qa’ida — the group responsible for the 9/11 attacks — fueled by recruitment efforts through Twitter and social media that have led to a spike in arrests in the past few months. Speaking last week at a national security conference at Aspen Institute, the director said the Islamic State, known variously as ISIS or ISIL, has become especially effective at recruiting impressionable and “troubled souls” by pushing its message “all day long” through Twitter and other social media. Since March 2014, at least 58 men and woman have been charged with conspiring to aid ISIS, the deadly terror group that now controls a large swath of territory in Syria and Iraq, according to the Center on National Security at Fordham Law. Those numbers have soared in recent months, with 42 cases filed in US courts this year alone. Here in the metropolitan area, four men have charged in related cases filed by the US Attorney’s offices in Newark and in Brooklyn filed in June. Richard Frankel, who led the FBI’s Counterterrorism Division in New York and now head of the bureau’s Newark office, said the rapid expansion of social media such as Twitter, YouTube and Facebook has allowed disaffected individuals to fall under the spell of othersand made it far more difficult to catch them. “It’s become easier to radicalize. You can do it online,” Frankel said. “Before, if you wanted to talk to a terrorist, you had to email someone like (Anwar) AlAwlaki. Now you can find them through Twitter.” While the FBI can get court-approved access to Twitter exchanges, FBI officials said it cannot easily break encrypted communications on the social media site. According to Frankel, all 56 FBI field offices are now working terrorism cases. In a recent study by the Center on National Security, researchers found most arrested in this country on ISIS-related charges were US citizens. Most were in their early 20s and a third were late converts to Islam. Surprisingly to researchers, 15 percent were women. And eight out of 10 cases involved recruiting on behalf of ISIS through social media, or communications sympathetic to ISIS.