The lethality and frequency of international terrorism has declined steadily since 2014, although militant jihadist ideology continues to inspire “homegrown” terrorists in the United States and elsewhere. Today, there is growing concern in many countries about domestic terrorism, most of it at the hands of white supremacists and nationalists. The U.S. Department of Homeland Security now includes white supremacist violence on its list of priority counterterrorism targets, and Congress is considering legislation making domestic terrorism a federal crime. Some believe President Trump’s rhetoric encourages extremist violence, an accusation he vigorously denies. Meanwhile, the U.N. secretary-general has declared cyberterrorism — using social media and hidden internet sites to spread propaganda, recruit followers and coordinate attacks — the “new frontier” among global threats, and major tech firms have joined to battle them.