AQAP, the Lone Jihad affiliate in the Yemen, is widely viewed as the most violent of the lot; so when its leader, Ibrahim al-Asiri, singles out US lone-wolf attacks for praise and calls for more of them, the US security forces are right to be concerned. Al-Asiri is believed to be developing a 'new generation' of wearable explosive devices (shoes, underwear etc.).
AQAP, the Al Qaeda affiliate in the Yemen, is widely viewed as the most violent of the lot; so when its leader, Ibrahim al-Asiri, singles out US lone-wolf attacks for praise and calls for more of them, the US security forces are right to be concerned. Al-Asiri is believed to be developing a 'new generation' of wearable explosive devices (shoes, underwear etc.).