Abu Sayyaf is a violent extremist group that split from established Philippines separatist movement Moro National Liberation Front in 1991. It was formed by Abdurajak Abubakar Janjalani, who trained in the Middle East and reportedly met with al Qaeda leader Osama bin Laden.
The Philippines is a predominantly Catholic country, but the south has historically had a large Muslim population. Abu Sayyaf's stated aim is to establish an independent Islamic state on the southern island of Mindanao.
The group first became active in the early 1990s and was responsible for bombings across the southern Philippines and in the Malaysian state of Sabah.
Following the 9/11 attacks, Washington worked hard with the Philippine military to try and stop the group's terrorist activities.
Largely weakened by these attacks, Abu Sayyaf started to move from large-scale bombings to kidnappings, a move many analysts see as more profit-driven and criminal in intent.
"But after about 15 years of a pretty harsh crackdown by the U.S. and the Philippines, what they've basically become is a criminal group made up of a few hundred who engage in extortion and kidnapping."
Poling said the group is now largely fragmented, with around 200 to 400 members, and lacks the popular support base it enjoyed in the early 1990s.
"This is basically a group of criminals whose only support comes from family connections in the local communities," he said.
ISIS affiliation?
Abu Sayyaf reportedly was trained and funded by al Qaeda and Indonesia-based militant group Jemaah Islamiyah at the outset, but this well-publicized connection to established overseas Islamist extremist groups remains tenuous.
Abu Sayyaf was inspired by al Qaeda and has undoubtedly received financial support from overseas extremist groups in the past, but there's no evidence of such support today, Poling said.
"There's still no direct evidence of support or funding from IS (ISIS) of anything beyond the, I guess cache, that Abu Sayyaf, or some members of Abu Sayyaf, felt like they got from this public swearing," he said.
Are there other hostages?
Robert Hall and Marites Flor are among Abu Sayyaf's hostages.
Can Abu Sayyaf be defeated?
However, he said significant inroads have been made in reducing its membership and many of its leaders have been killed, including the group's founder, Janjalani, in 1998.
A national Philippines court also declared the group a terrorist organization under a rarely used law in 2015, effectively outlawing membership.
However, Poling said obstacles remain in eradicating the group completely, including the weakness of the Philippine military across much of the south, the porousness of the region's borders with Malaysia and Indonesia, and its remote geographic location.
"Once they get into the jungles of Mindanao, there's a saying that the Philippine state controls the roads and others control the countryside down there," he said.
Renewed international attention may help overcome these roadblocks, but it may be of little consolation to those who remain hostages under Abu Sayyaf in the jungles of Mindanao.
CNN Philippines contributed to this report.
