Wednesday’s attack on a satirical newspaper in Paris prompted speculation about the involvement of an organized terrorist group, possibly the Islamic State, whose leaders have called for sympathizers to carry out assaults wherever they can. These “lone wolf” attacks have included the siege of a cafe in Sydney, Australia, last month; an attack on the Jewish Museum in Brussels in May; and a gunman’s rampage through the Parliament building in Ottawa in October.

Even as French and other Western intelligence and counterterrorism officials said they had not yet determined which extremist groups, if any, might have been involved in the attack in Paris, some veteran analysts and terror experts suggested that Al Qaeda or one of its affiliates might be implicated.