The Nigerian militant group Boko Haram has pledged allegiance to ISIS , according to a message posted online allegedly from Boko Haram's leader, Abubakar Shekau.

The pledge is a move that may signal ISIS' transformation into an organization with global reach, said Charles Sennott, cofounder of GlobalPost and head of The GroundTruth Project .

"I do think the Islamic State is beginning to think the way al-Qaida did when it became a franchise, that they sought to replicate," Sennott said.

"It's hard to think of a death cult as having a business plan and a marketing strategy, but I think that is literally what it is," he continued. "They are very sophisticated in the way they put out the call to young Muslims to come and fight against the enemies of Islam."

Sennott said to combat that strategy would require sophisticated counter-messaging from the United States and its allies, especially online, where ISIS does much of its recruiting. For now—though an unsettling development—it's unclear how a pledge from Boko Haram to ISIS will impact how both organizations operate.

"They're disconcerting," Sennott said of the pledges.  "They mean the cancer has metastasized further."

"I think we have to watch it carefully, but I don't think anyone knows yet what it will look like on the ground, practically, in Nigeria," he continued.

To hear more from Charles Sennott, tune in to the full segment from Boston Public Radio above.