The Islamic State-inspired attacks in Jakarta on 14 January 2016, the 9 April 2016 attack on Philippine security forces in the southern island of Basilan conducted by groups claiming allegiance to IS, and a spate of kidnappings by known terrorist groups in the southern Philippines serve to remind us of the persistent threat that terrorism continues to pose to Southeast Asia. While terrorism isn’t a new security phenomenon in Southeast Asia, over the past year, IS has emerged as the preeminent signal expression of the terrorist threat within the region. That’s partly due to the speed with which the group has gained popularity in the region and the number of local terrorist groups that are now claiming allegiance to their ideology.

Estimates of the number of Southeast Asians now fighting with IS and other smaller militant groups in Syria and Iraq vary significantly but are likely to hover around 1,000. The clear majority come from Indonesia, followed by Malaysia and a handful are known to be Singaporeans and Filipinos. While these figures are a fraction of the populations of the region, the IS phenomenon nevertheless poses several problems for regional countries.

First, there’s the direct threat posed by attacks undertaken by local networks or individuals inspired by IS. Second, there’s the growing threat posed by returnees from Syria and Iraq. In particular, authorities are concerned about the operational experience and influence among local jihadists that these individuals potentially possess. Third, there’s a potential threat posed by militants who are soon due to be released from prison for terrorist related offenses. Weak prison systems in countries such as Indonesia and the Philippines mean that terrorists may continue to associate with their networks and even plan attacks while in prison, as well as radicalise other prisoners that they frequent with.

While Jemaah Islamiyah (JI) is Indonesian based and focused, it has had significant influence and impact across Southeast Asia, particularly in Malaysia, Singapore and the Philippines. The emergence of JI at the turn of the century thrust the threat of terrorism to the forefront of regional states’ security agendas, where it has remained. Yet the threat itself has morphed from the more organised and hierarchical structure of JI to an atomised and virulent ideology of IS in recent years (although the JI threat hasn’t dissipated). When Abu Bakr al-Baghdadi announced on 28 June 2014 (the first day of Ramadan) that a caliphate had been formed by IS in Syria and Iraq, the announcement captured the imagination of the extremist fringe across Southeast Asia.

In September 2014, the Southeast Asian dimension of the group was given something of a formal expression with the formation of Katibah Nusantara, an IS wing consisting of Malay- and Indonesian-speaking fighters in Syria. Katibah fulfils several functions: it provides a social network to help Southeast Asian recruits and their families settle in, training for those who’d eventually take up arms and communications with the network of pro-IS groups operating in Syria. These developments and links demonstrate that the threat posed by IS in Southeast Asia is real, and that it has been growing since mid-2014. The changing nature and manifestation of the threat means that counterterrorism responses have had to evolve accordingly.

Over the past year, national security operations have gathered pace in maritime Southeast Asian countries as leaders call for vigilance against the threat posed by terrorism. Notwithstanding the increased counterterrorism effort, several challenges remain both for individual states and for the region as a whole. There are five key issues that should be considered.

The first is how Southeast Asian governments have addressed a range of matters relating to extremism, including how the politicisation of Islam is dealt with in relation to extremism, hate speech and violence against minorities. Second, greater effort is needed to acknowledge both the severity of the problem and the shortcomings of existing CT efforts. A third challenge is the issue of military professionalism and security sector reform especially in the Philippines. Fourth, given the transnational nature of the problem, improvements in governance and security sector reform at the national level would still need to be supplemented with broader and deeper regional cooperation to effectively deal with the threat. Fifth, regional governments must be cognisant of the fact that religious rehabilitation to counter violent extremism, while important, has its limits.

In 2017, the threat of terrorism will continue to preoccupy security agencies in the region, and they must be prepared to respond to three main concerns. First, returning Southeast Asian foreign fighters must be dealt with. With the turning of the tide against IS in Syria and Iraq in recent months, it’s likely that some of these fighters will be finding their way home, some of them intent on continuing their armed jihad on local shores. Second, there’s the real prospect that the southern Philippines could be identified as a safe haven for Southeast Asian jihadists. Third, while JI continues to be at odds with IS affiliates, it would be foolhardy to dismiss the prospects for rapprochement, leading to some sort of tactical cooperation.