Since Jan. 1, at least 100 locations of Jewish organizations in the United States — including schools, Jewish Community Centers, and offices of the Anti-Defamation League — have received a total of 134 bomb threats. The majority have come in five of what the JCC Association of North America calls “waves” — groups of robocalls coming on a single day. So far, none of the threats have been carried out. In late November, Marna Street, a violist with the Cincinnati Symphony Orchestra, was walking to her car after a rehearsal. Street was shocked by what she discovered: Someone had painted a swastika, about 14 inches across, on the trunk of her car.