It is reported that they recently began expanding into neighbouring Malaysia and Indonesia. The group is responsible for bombings, assassinations, kidnappings, and extortion in order to promote an independent Islamic state in western Mindanao and the Sulu Archipelago and create an atmosphere conducive to the creation of a Pan-Islamic superstate in the Malay portions of South-east Asia. The name of the group is Arabic for Father (Abu) of the Sword (Sayyaf).
The ASG is the one of the smallest and arguably the most radical and dangerous of the Islamic separatist groups in Mindanao. Some ASG members have studied or worked in the Saudi Arabia and developed ties to muhajadeen while fighting and training in Afghanistan and Pakistan.
Members of the ASG were once part of the Moro National Liberation Front, but started on their own in 1991 under the leadership of Abdurajik Abubakar Janjalani.
After Ramzi Yousef bombed Philippine Airlines Flight 434, killing a Japanese passenger, a man stated in a telephone call "We are Abu Sayyaf Group. We explode one plane from Cebu." The bombing was supposedly a test for Operation Bojinka, which was discovered by Manila police on January 6, 1995.
Abu Sayyaf's first large-scale action was the beachhead asault on the town of Ipil in Mindanao in April 1995. It is responsible for the kidnapping and murder of more than 30 foreigners and Christian clerics and lay-workers.
The death of Aburajik Abubakar Janjalani, otherwise known as Abu Sayyaf, marked a turning point in ASG operations, shifting from its ideological focus to more general kidnappings, murders and robberies.
The ASG primarily operates in the southern Philippines with members occasionally traveling to Manila, but the group expanded its operations to Malaysia in 2000 when it abducted foreigners from two different resorts. A commander named Abu Sabaya was killed in 2002 while trying to evade forces. See . Galib Andang, aka Commander Robot, was captured in Sulu in December 2003. 
Abu Sayyaf is estimated to have a core membership of 200 with an extended membership of over 2000.
The group was originally not thought to receive funding from any government, but intelligence reports from the United States, Indonesia, and Australia have found intermittent ties to the Indonesian Jemaah Islamiyah terrorist group.