Abu Musab al-Barnawi is about 25 years old and the second son of Mohammed Yusuf, who founded the group in 2002, the source told CNN. Mohammed Yusuf was captured and executed after a clash with Nigerian security forces in 2009.
The insider said there was a split in the ranks of the Boko Haram terror group three months ago, which led to Barnawi, known as Habib Yusuf within the group, to leave the Sambisa forest where Boko Haram are believed to be hiding out.
He re-emerged this week after he was introduced as the new leader of the terrorist sect in an interview in the ISIS' magazine al-Naba. Boko Haram has long had links with ISIS, pledging allegiance to the group in March.
Even though Barnawi is now supposedly the leader of Boko Haram, the source told CNN that the group's long-time leader Abubakar Shekau still has the larger number of followers in the Sambisa forest and crucially has control of the abducted Chibok schoolgirls. The schoolgirls are seen as a powerful bargaining chip for the terrorist group, whose base has been significantly weakened.
Western intelligence sources close to negotiations believe, however, that the defection of manpower and erosion of support leaves Shekau more exposed and could possibly lead to a breakthrough in the search for the abducted girls.
The Boko Haram source told CNN that Barnawi was Boko Haram's head of armory before he fell out with Shekau and left with some followers. The source said: "Shekau is seen as erratic and disorganized and Habib didn't agree with a lot of his decisions anymore."
According to the source, Barnawi left the base in the Sambisa with another Boko Haram commander, Mamman Nur, who is suspected by Nigerian authorities of carrying out the 2011 bombing of the UN building in the country's capital, Abuja.
In 2011, Barnawi's mother and elder brother were killed in a bombing in Kano, the source said.
Adding to the confusion, Abubakar Shekau broke his silence Wednesday. He challenged the new leadership announcement in a 10-minute audio message posted on YouTube to let everyone know he was "still around."