The name of the group is derived from the Arabic abu (أبو) ("father of"), and sayyaf (سيّاف) ("swordsmith"). As of 2012, the group was estimated to have between 200 and 400 members, down from 1,250 in 2000. They use mostly improvised explosive devices, mortars, and automatic rifles.
Since its inception in 1991, the group has carried out bombings, kidnappings, assassinations, and extortion in what they describe as their fight for an independent Islamic state in the Philippines. They have also been involved in criminal activities, including kidnapping, rape, child sexual assault, forced marriage, drive-by shootings, extortion, and drug trafficking, and the goals of the group "appear to have alternated over time between criminal objectives and a more ideological intent".
The group has been designated as a terrorist group by the United Nations, Australia, Canada, Indonesia, Malaysia, the Philippines, United Arab Emirates, the United Kingdom, and the United States. In 2002, fighting Abu Sayyaf became a mission of the American military's Operation Enduring Freedom and part of the Global War on Terror. Several hundred United States soldiers are also stationed in the area to mainly train local forces in counter terror and counter guerrilla operations, but, as a status of forces agreement and under Philippine law, they are not allowed to engage in direct combat.
The group was founded by Abdurajik Abubakar Janjalani, and led after his death in 1998 by his younger brother Khadaffy Janjalani who was killed in 2007. On 23 July 2014, Abu Sayyaf leader Isnilon Hapilon swore an oath of loyalty to Abu Bakr al-Baghdadi, the leader of ISIL. In September 2014, the group began kidnapping innocent people for ransom like recording them beheaded if their demands are not met, in the name of ISIL.