Change, Continuity and Trajectories: Assessing Southeast Asian Terrorists’ Attack Tactics and Trends Post-Bali Bombings
Since the 2002 Bali bombings, Southeast Asian militants’ tactics have experienced both transformation and continuity. Militant groups have used bombs to inflict heavy casualties and firearms to defend territory. At the same time, stabbings have also become more prevalent. In recent years, the increased diversification of terrorist tactics, illustrated by women and children’s involvement in suicide bombings in the Philippines and Indonesia, has accrued to factors such as intensified counter-terrorism operations, the availability of weapons suppliers and tradecraft manuals online, and the influence of Al-Qaeda (AQ) and Islamic State (IS) Central. Going forward, terrorists will continuously adapt their modus operandi amidst evolving operational environments.
The 2002 Bali bombings were one of Southeast Asia’s earliest and most devastating terrorist attacks. Since the Jemaah Islamiyah (JI)-linked suicide attacks, which killed around 202 people and injured 209 others, security authorities and various terrorist groups in Southeast Asia have evolved and upgraded their operational capabilities. This study revisits the evolution of Southeast Asian terrorist groups’ modus operandi and the attendant counter-terrorism (CT) responses over the past two decades.
In the aftermath of the Bali bombings, JI continued to play a pivotal role in shaping the jihadist landscape in the region up until the late 2000s. JI operatives leveraged networks formed during their stints as Afghan mujahideens to establish long-term ties with Al-Qaeda and regional militant groups such as the Moro Islamic Liberation Front (MILF) and the Abu Sayyaf Group (ASG). From the mid-2010s onwards, the rapid emergence of the so-called Islamic State (IS) in 2014 re-energised violent extremism in the region.
However, widespread clampdowns in recent years have led to the suppression or splintering of JI and other IS-linked organisations. This has resulted in changing trends and shifts in the attack tactics of jihadist groups in Southeast Asia.
Explosives and Bomb Plots
The use of improvised explosive devices (IEDs) is most frequent in the Southeast Asian militant landscape. Before IS’ emergence, IEDs were often deployed against Western targets. Consistent with AQ’s narrative of the time, IED attacks aimed to evict “Western influence” from Muslim lands, including Indonesia. As shown in Table 1, IED attacks in the region have mostly been conducted at high-traffic tourist areas, or places with Western diplomatic representation.
Table 1: Terrorist Plots and Attacks Between 2000-2009
|30 December 2000||Rizal Day bombing||Philippines||Diplomats, Tourists||22||~100|
|December 2001||Singapore Embassy plot||Singapore||Diplomats||Foiled|
|Super Ferry 14 bombing||Philippines||Tourists||116||Unknown|
|Australian Embassy bombing||Indonesia||Diplomats||10||100|
|1 October 2005||Bali bombing||Indonesia||Tourists||26||102|
|17 July 2009||Jakarta bombing||Indonesia||Tourists||9||53|
With the pivot from JI to IS in Southeast Asia since the early 2010s, attack targets and tactics have also evolved. For instance, bomb plots have become more frequent and indiscriminate, while also less sophisticated and lethal. Figure 1 plots the number of IED attacks and attempts from 2014 to 2021, based on the Southeast Asia Militant Atlas (SEAMA) database.
According to Figure 1, since 2014, most of the bombings in Southeast Asia have been foiled by the authorities. Only 28.22 percent (57 incidents) of attempted bomb plots were successful between 2014 and 2021. Most bomb plots were foiled through the arrests (51.98 percent) and killings (9.90 percent) of would-be perpetrators. As many as 20 attacks (9.90 percent) are categorised as “Failed” attacks, as the only casualties were the perpetrators themselves. From the graph above, it can be observed that bombings spiked exponentially in the second quarter of 2019 with a total of 27 incidents, but only 3 successful attacks were recorded.
IEDs deployed by terrorists have mostly used ammonium nitrate as the primary charge. The 2018 Lamitan attack in the Philippines highlighted a potential innovation in ammonium nitrate bombs, as ASG used a 10-seater van to deploy the bomb and the vehicle’s fuel for its detonation. Among JI militants in Indonesia, TNT (trinitrotoluene) extracted from potassium chlorate or black powder was previously the primary choice of explosive.
However, following the 2003 J.W. Marriott hotel bombing, the authorities enhanced surveillance of the procurement of black powder. Triacetone triperoxide (TATP) then emerged as the substitute to TNT and gunpowder.
TATP was first used in a terrorist attack in Southeast Asia on 28 October 2015 in Indonesia. The IS-inspired attacker detonated a bomb at the Alam Sutera Mall in Tangerang. Since then, numerous IS-linked Jamaah Ansharut Daulah (JAD) members have been arrested for attempting to make TATP. TATP was also used in the 2016 Movida Nightclub bombing in Malaysia and the 2018 Surabaya Church bombings in Indonesia. Today, TATP is still widely used by IS-linked groups in Indonesia, but has yet to be deployed in the Philippines.
Gunfights and Territorial Control
Guns appear to be militants’ preferred weapon for defending their territorial strongholds. This trend is consistent across time. From JI’s involvement in Poso (2003-2008), to the long-running Mindanao insurgency (1969 to present), guns have been used to hold territory. There have also been instances of guns being used outside territorial strongholds.
In some instances, access to firearms has boosted the morale of terrorist cells when motivation might have waned. This was the case for JI’s Palembang group. Based on a May 2009 report by the International Crisis Group, a JI cell in Palembang, South Sumatra, had been unmotivated to conduct attacks due to repeated failed attempts. However, access to guns would prove to be an important factor in the group later mounting a series of attacks, including the killing of a Christian teacher. Another incident involving the use of guns was the January 2016 attack at the Sarinah Mall and a Starbucks coffee shop in Jakarta.
Arguably, the defensive properties of firearms have compelled terrorists to use them to defend territory. Figure 2 (from the SEAMA database) shows that guns were used almost exclusively in territorial strongholds between 2014 and 2021. The hotspot analysis conducted by the authors aggregates the areas where gunfights occurred and highlights the territorial strongholds of each terrorist group. Essentially, it was found that terrorist groups with greater access to automatic firearms are more likely to hold their territory.
|Philippines||Lanao, North Mindanao||Dawlah Islamiyah-Maute Group|
|Philippines||Maguindanao, Central Mindanao||Bangsamoro Islamic Freedom Fighters|
|Philippines||SocSarGen, South Mindanao||Ansar Khilafa Philippines|
|Philippines||Basilan, West Mindanao||Abu Sayyaf (Dawlah Islamiyah Basilan)|
|Philippines||Sulu, West Mindanao||Abu Sayyaf (Dawlah Islamiyah Sulu)|
|Indonesia||Poso, Central Sulawesi||Mujahideen Indonesia Timur|
Figure 2: Guns in Southeast Asia (top), Hotspot Analysis (middle) and Territory-Terrorist Nexus (bottom)
Stabbing and slashing attacks have been witnessed in Indonesia, and were mainly perpetrated by IS-linked networks. Between 2014 to 2021, 24 incidents in Indonesia involving the use of sharp weapons, such as machetes, swords and knives, were recorded. Comparatively, JI has only conducted five attacks using sharp weapons since its inception. The use of such weapons in attacks is coherent with IS’ appeal for immediate jihad. In its propaganda, IS argues that anyone can conduct jihad with household objects. Besides conventional bladed weapons, IS-influenced perpetrators have used common household items like scissors to stab their victims.
Two incidents in recent years illustrate this trend. In 2018, two teenage sisters, Dita Siska Millenia and Siska Nur Azizah, were arrested for planning to stab police officers with scissors. However, the first successful attack involving the use of sharp objects was the stabbing of Indonesia’s then Coordinating Minister of Political, Legal and Security Affairs, Wiranto, in October 2019. The couple involved, Syahril Alamsyah and Fitri Andriana, stabbed the Minister with a pair of scissors and a kitchen knife after he had alighted from his vehicle en route to an event. Besides bladed ambushes, IS affiliates have also conducted beheadings. Notably, the Abu Sayyaf (Dawlah Islamiyah Sulu) in the Philippines and Mujahidin Indonesia Timur (MIT) in Indonesia have kidnapped and beheaded civilians when their ransom demands were not met.
Families have played an important role in facilitating terrorism in the Southeast Asian context. Traditionally, terrorism has been perceived as a masculine endeavour, and women have played nurturing roles in threat groups. Female jihadists from JI had, for example, served as couriers during the Maluku and Poso conflicts from 1998 to 2002. But JI’s Women Wing also participated in dakwah (Islamic preaching), showing that women also played a strategic role in education and recruitment. Moreover, women hold an important position in maintaining a movement’s secrecy. Many wives of JI members have taken steps to hide their husbands, other operatives and weapons from law enforcement.
Yet, since IS began to dominate the Southeast Asian threat landscape from the mid-2010s onwards, more militant jihadist women have transcended their traditional roles. Today, female IS supporters are more actively engaged as enablers of terrorism via recruitment and fund-raising activities. Ika Puspitasari is an example of a female recruiter, financier and (would-be) perpetrator. She recruited her husband, Zaenal Akbar, to coordinate an attack in Indonesia, and contributed Rp 8 million (US$ 600) to fund it. After being deported from Hong Kong, where she had been employed, she also planned to carry out a suicide bombing in Bali in 2016. Other examples include Rafiqa Hanum, the wife of Bahrun Naim, who recruited two Indonesian males to migrate to Syria; and Tutin Sugiharti, a fund-raiser who collected money to support the wives and children of pro-IS inmates in Indonesia.
Moreover, IS female militant jihadists have also engaged in operational roles such as suicide bombers and knife attackers. This includes the wives of MIT militants, who participated in combat training, such as shooting practice and physical conditioning, in the Poso jungle in preparation for active combat. Women have also featured as attack planners. In 2016, Dian Yuli Novi plotted a suicide attack at the Indonesian Presidential Palace in Jakarta. The Wiranto stabbing in 2019 also featured a female assailant, the then 21-year-old Fitri Andriana.
An additional concern has been the mobilisation of entire families for terrorist attacks. Some Southeast Asian militants who made hijrah (migration) to Iraq and Syria brought their families, including their children, along with them. Some of these children were later deployed as child suicide bombers on the Syrian battlefield at the instruction of their parents. These included the sons of current and former JI members, Imam Samudra and Syaiful Anam, respectively.
Chemical, Biological and Radiological Weapons
There have been some attempts at tactical innovation by regional terrorists, including developing Chemical, Biological and Radiological (CBR) capabilities. Malaysian national and founding member of JI, Yazid Sufaat, attempted to cultivate anthrax for AQ in 2001. While it is unclear if Yazid planned to release anthrax in Southeast Asia, his biochemistry background meant he was able to leverage his networks and resources to acquire ammonium nitrate for Fathur Rahman al-Ghozi, JI’s expert bomb-maker.
While pro-IS groups have yet to develop operational CBR weapons, they have expressed interest in exploring alternative weaponry. This is evinced by a 2015 plot by Indonesian returnees from Syria who attempted to detonate a chlorine bomb; the possession of a radiological dispersal device with Uranium-233 by a JAD cell in Bandung in 2017; and a JAD-linked suicide plot in 2019 involving the use of a bomb containing abrin poison.
Overall, unlike JI, pro-IS militants in Southeast Asia seem to prefer ad hoc, impromptu attacks over large-scale operations with detailed drawer plans. These militants also appear to be less adept in their tactical prowess (multi-phase attack planning, bomb-making, CBR capabilities etc.), and more interested in overwhelming the authorities with frequent but ill-planned attacks.
Vehicle Ramming and Drones
Vehicle-ramming and drone attacks are another tactic of concern. While Southeast Asian states have yet to encounter a vehicle-ramming incident involving civilians, there have been cases of car and motorcycle bomb plots. A potential explanation for the absence of vehicle-ramming incidents may be the traffic congestion that bedevils many high-density cities in Southeast Asia, which may render such attacks harder to pull off or result in failed plots being disguised as traffic accidents.
However, terrorists in the region have attempted to use drones on two occasions. The first case involved a Malaysian factory worker, Mohammad Firdaus Abdullah. In 2016, he suggested flying an IED-laden drone over the Malaysian Police Headquarters in Bukit Aman and a Freemason Lodge in Bukit Jalil. Drones were also used for surveillance. During the 2017 Marawi Siege, IS militants had piloted a commercial quadcopter to survey the battlefield. Despite the infrequent use of drones thus far, it is likely that militants will pounce on the technology whenever the opportunity arises.
Overall, terrorist activities have largely declined during the COVID-19 pandemic. Based on the SEAMA database as reflected in Figure 3, the frequency of violent terrorist activities increased consistently from 2014 to 2019, but there was a steep drop in the first quarter of 2020. This trend was followed by high rates of arrests of and surrenders by militants in both Indonesia and the Philippines. The authorities’ ability to conduct effective counter-terrorism has arguably improved during the global pandemic.
However, as the region normalises with the lifting of tight border controls and improvements in the economy, the CT gains made by the authorities need to be bulwarked with security and policy responses to the following developments in the regional radical landscape.
Modus Operandi – Variety and Preference
IEDs will remain the preferred bombing tactic employed by jihadist groups in the region for two reasons: a) access to explosive materials and b) bomb-making manuals. Explosive compounds can be distilled from common household items, or conveniently procured in certain industries. For example, ammonium nitrate can be distilled from fertilisers, while TATP can be concocted using chemicals readily available in hardware stores.
Moreover, chemical substitutes of explosives have been identified on open markets. Militants have also purchased explosive materials online to avoid suspicion from brick-and-mortar sellers. Furthermore, militants have avoided bank transfers when making payments to evade detection – instead, bomb-makers have leveraged the various money transfer services available in convenience stores to make online payments.
Manuals on how to make bombs are also widely available on the internet, allowing people to potentially become autodidactic bomb-makers. Abu Hamzah, a JAD member from Sibolga who made 300 kilograms of explosive materials with his wife, reportedly learned how to make a bomb from the internet. Maswandi, another JAD member from Batang, Central Java, also succeeded in creating a mobile detonator for his bomb by learning from video tutorials on Bahrun Naim’s website. The ease of access to explosive materials and manuals arguably makes bombings the preferred tactic for jihadists in the region, particularly in Indonesia.
In Indonesia, the role of the bomb supplier is essential for those who are unable to make their own explosives. One individual known as KDW (initials), alias Abu Aliyah al-Indunisi, sourced and supplied bombs to at least four different groups from 2016 to 2021. One of them was the JAD couple who conducted a suicide bombing at a Makassar church in 2021. Semi-automatic guns have also been used frequently by terrorists in the region. While guns are mostly used to hold territory, particularly in Mindanao and Poso, they have also been used in urban areas, like during the 2016 Sarinah Mall attacks.
There has also been an increase in the use of bladed weapons in recent years, involving knives, machetes and scissors. Bladed weapons have also been used alongside other weapons. Ivan Armadi Hasugian and Suliono, for example, had carried IEDs while conducting mass stabbings in 2016 and 2018, respectively.
Despite the significant increase in the use of bladed weapons, they still constitute a minority of the attacks perpetrated by terrorists in the region. For security agencies in Indonesia and the Philippines, it can be challenging to regulate bladed weapons, given that machetes, for example, are common tools found in many households and are essential to the locals’ daily lives. At any rate, CT agencies must train themselves to be situationally aware of an edged weapon attack.
At present, guns and explosives are still overwhelmingly favoured by terrorists in this region. To stem their ability to procure firearms, authorities should enhance border controls over routes known to be used by weapons smugglers, such as in North Sulawesi and East Kalimantan, and shut down illegal weapons assembly factories. In terms of explosive materials, although much has already been done to minimise the unlawful acquisition of black powder, authorities should also consider monitoring the supply of TATP ingredients like acetone and hydrogen peroxide, which are currently readily available at hardware stores.
Strategy – Jihad Now or Jihad Later
The will to enact terror persists. Groups such as JI are currently committed to the “jihad later” strategy. Its adoption of this strategy does not, however, mean that JI has abandoned the violent path. Rather, the group has focused on building its capabilities in dakwah (religious outreach), i’dad (physical training), pengajian (religious education) and fund-raising, until it has gained sufficient operational capacity. Despite being leaderless for two years, JI militants remain committed to posing a long-term security threat to Indonesia, and potentially the wider region. JI could plan for a more lethal attack, as the group possesses superior military capability, political strategy and economic resources, compared to pro-IS groups.
Though JI has a more developed strategy, pro-IS groups remain a threat to the region given the “jihad now” mentality of its followers. In recent years, ASG has continued its attempts to disrupt civilian lives with IED attacks. The leader of the Philippines’ Dawlah Islamiyah-Maute Group, Abu Zacariah, also continues to operate in Lanao province. In early 2021, Anshar Daulah Gorontalo, a small pro-IS group, planned to attack police headquarters in Gorontalo, Sulawesi. In June 2022, Indonesian law enforcement also discovered that JAD’s Bima cell in West Nusa Tenggara have continued their physical and weapons training. Ultimately, these recent developments indicate that the appeal of pro-IS groups persists in the region.
Indonesian security agencies have taken comprehensive steps to curtail JI’s long-term and non-violent threat. In 2021 alone, Densus 88 arrested 339 suspected JI members and sympathisers, including high-profile figures and preachers such as Abu Rusydan, among others. Despite proactive enforcement efforts, however, the authorities still face significant challenges against the backdrop of the more exclusivist religious milieu which has emerged in Indonesia in recent years. For its part, JI remains focused on its Tamkin Siyasi (political consolidation) strategy to secure support for its cause from the wider Muslim community in Indonesia, as a complement to its current “jihad later” strategy.
To address the threat posed by JI as well as pro-IS networks, authorities in Indonesia and around the region should strengthen their operational clampdowns as well as the various deradicalisation and counter-narrative initiatives, which address both exclusivist and extremist ideologies, and the socioeconomic drivers that often fuel terrorist recruitment. They will also need to monitor the mainstreaming of radical ideas in their respective societies, such as in collaborations between political parties and radical groups.
This will require, in part, the fostering of a regional ecosystem which rejects radical ideas and consistently upholds an inclusive and moderate Islamic narrative in initiatives by both grassroots movements and governments. To this end, amidst competing pressures on national budgets due to the pandemic and other global security concerns, some countries will need to demonstrate their political support of and commit economic resources toward CT-related programmes.
Families and Women as Perpetrators
In addition to buttressing other CT measures, it is necessary to develop more programmes regionally to increase engagement with women in their multiple roles as wives of terrorists and radicals, mothers of at-risk youth, and active agents of radicalism. The Organization for Security and Co-operation in Europe argues that the engagement of women is “essential to address the conditions conducive to terrorism and effectively prevent terrorism”. Just as terrorists have exploited women to nurture or enable future terrorists, or conduct violence themselves, policymakers can combat radicalisation with more women-centred programmes. The latter can delve into how women can be positive parental or spousal influences, or explore how to redirect the underlying motivations for females who adopt a violent jihadist orientation toward more beneficial causes.
Overall, the broad tactical and strategic trends of Islamist terrorism in Southeast Asia have evolved in the aftermath of the Bali bombings, notwithstanding the differences between key regional terrorist groups aligned to AQ or IS. These current tactics and strategies continue to represent a threat to the security of countries in the region, and will require effective and holistic responses from both security agencies and civil society organisations. Guns and bombs are still the weapons of choice for terrorist groups, with guns favoured for territorial defence. While there has been a significant increase in the use of bladed weapons following the rise of pro-IS groups in Southeast Asia beginning in the mid-2010s, they still constitute the minority of attacks and plots. Moreover, pockets of individuals remain keen to experiment with CBR weaponry, although interest in engaging in such tactics remains minimal. The involvement of families and women in regional radicalism is likely to remain an operational option, especially for IS-affiliated groups.
About the Authors:
Kenneth Yeo and Unaesah Rahmah are senior analysts at the International Centre of Political Violence and Terrorism Research (ICPVTR), a constituent unit of the S. Rajaratnam School of International Studies (RSIS), Nanyang Technological University (NTU), Singapore. They can be reached at [email protected] and [email protected], respectively.
Thumbnail photo by Matt Hearne on Unsplash
 The two-stage attack, which concluded with the detonation of a military-grade explosive-laden van along a densely populated area in the tourist district of Kuta on Bali Island, was facilitated by Riduan Isamuddin (alias Hambali), who received funding from Al-Qaeda to launch the suicide bombings. See “’Al-Qaeda Financed Bali’ Claims Hambali Report,” The Sydney Morning Herald, October 6, 2003, https://www.smh.com.au/national/al-qaeda-financed-bali-claims-hambali-report-20031006-gdhjab.html.
 The Bali bombings were the precursor to other high-profile attacks. Refer to Table 1 for a list of attacks conducted by Jemaah Islamiyah from 2000 to 2009.
 Many JI members participated in the 1979 Soviet-Afghan War to support the Afghan resistance. They later became known as the “Afghan Alumni” or “Afghan Veterans” upon returning to Southeast Asia.
 Ministry of Home Affairs Singapore, The Jemaah Islamiyah Arrests and the Threat of Terrorism: White Paper (Singapore: Ministry of Home Affairs, 2003), https://eresources.nlb.gov.sg/printheritage/detail/2125a7b0-9a25-47ca-bf7f-a74a41a4261b.aspx.
 Kenneth Yeo and Unaesah Rahmah, “Southeast Asia Militant Atlas,” S. Rajaratnam School of International Studies: International Centre for Political Violence and Terrorism Research, December 8, 2021, https://www.rsis.edu.sg/research/icpvtr/southeast-asia-militant-atlas/#.YPjzf-gzaM8.
 Ammonium nitrate is generally distilled from fertilisers and mixed with petroleum or gunpowder before being deployed. Since this concoction is heavy and immobile, it is often used as a roadside bomb to ambush military vehicles.
 Amalina Abdul Nasir, “Islamic State Militants in Malaysia and Indonesia Increasingly Using High-End Explosives,” European Eye on Radicalization, December 10, 2019, https://eeradicalization.com/islamic-state-militants-in-malaysia-and-indonesian-increasingly-using-high-end-explosives/.
 Hanz Jimenez Salim, “Bom di Mall Alam Sutera Gunakan TATP, Pertama di Indonesia,” Liputan 6, October 29, 2015, https://www.liputan6.com/news/read/2352321/bom-di-mall-alam-sutera-gunakan-tatp-pertama-di-indonesia.
 Mei Amelia R, “Teror Mal Alam Sutera Pakai Bom, Leopard Terinspirasi ISIS,” Detik News, October 30, 2015, https://news.detik.com/berita/d-3057686/teror-mal-alam-sutera-pakai-bom-leopard-terinspirasi-isis.
 V. Arianti, “Indonesia Southeast Asia Country Assessments,” Counter Terrorist Trends and Analyses, Vol. 3, No. 1 (January 2011), pp. 5-9, https://www.rsis.edu.sg/wp-content/uploads/2014/09/CTTA-January11.pdf; Unaesah Rahmah, “More Terrorist are Using Guns in Indonesia,” Indonesia at Melbourne, July 1, 2020, https://indonesiaatmelbourne.unimelb.edu.au/more-terrorists-are-using-guns-in-indonesia/.
 International Crisis Group, “Indonesia: Radicalisation of the Palembang Group,” Asia Briefing No. 92 (May 20, 2009), https://reliefweb.int/report/indonesia/indonesia-radicalisation-palembang-group-icg-report.
 In this case, 14 gunmen stormed the mall, resulting in seven civilian deaths and 24 others injured. The assault lasted almost five hours. See Alex Johnson and Amalia Ahmad, “Indonesian Police Say Three Detained After Jakarta Attacks,” NBC News, January 15, 2016, https://www.nbcnews.com/storyline/isis-terror/indonesian-police-say-they-ve-arrested-three-jakarta-attacks-n496966.
 This was apparent during the 2017 Marawi Siege in the Philippines, when Islamic State militants used a variety of weapons, including guns, mortar and IEDs, to hold the territory for five months before their eventual defeat by the Armed Forces of the Philippines (AFP).
 Yeo and Rahmah, “Southeast Asia Militant Atlas.”
 Nur Aziemah Azman, “Evolution of Islamic State Narratives Amid the COVID-19 Pandemic,” Home Team Journal No. 10 (June 2021), pp. 188–96, https://www.mha.gov.sg/docs/hta_libraries/publications/home-team-journal-issue-10.pdf.
 Wahyudi Soeriaatmadja, “Indonesian Police Arrest 2 Women Planning to Stab Officers Using Scissors,” The Straits Times, May 13, 2018, https://www.straitstimes.com/asia/se-asia/indonesian-police-arrest-2-women-planning-to-stab-officers-using-scissors.
 “Indonesia Chief Security Minister Wiranto Attacked by Assailants With Knife,” The Straits Times, October 10, 2019, https://www.straitstimes.com/asia/se-asia/indonesia-minister-wiranto-attacked-by-assailant-with-knife-reports.
 Unaesah Rahmah, “The Role of Women of the Islamic State in the Dynamics of Terrorism in Indonesia,” Middle East Institute, May 10, 2016, https://www.mei.edu/publications/role-women-islamic-state-dynamics-terrorism-indonesia.
 Institute for the Policy Analysis of Conflict, “Mothers to Bombers: The Evolution of Indonesian Women Extremists,” IPAC Report No. 35 (2017), http://file.understandingconflict.org/file/2017/01/IPAC_Report_35.pdf.
 Rahmah, “The Role of Women of the Islamic State.” For example, Putri Munawaroh, the wife of Hadi Susilo, hid JI member Noordin M. Top and harboured firearms, ammunition and explosive materials in her house. See “Putri Munawaroh Terlibat Sembunyikan Noordin M Top,” Detik News, September 25, 2009, https://news.detik.com/berita/d-1208920/putri-munawaroh-terlibat-sembunyikan-noordin-m-top.
 Rizka Nurul, “Bom Medan, Ika Puspitasari dan Abu Hamzah,” RuangObrol.id, December 4, 2019, https://ruangobrol.id/2019/12/04/ulasan/analisa/bom-medan-ika-puspitasari-dan-abu-hamzah/.
 Dara Purnama, “Terungkap, Ika Puspitasari Calon ‘Pengantin’ yang Akan Ledakkan Bom di Bali,” Okezone News, December 22, 2016, https://nasional.okezone.com/read/2016/12/22/337/1573241/terungkap-ika-puspitasari-calon-pengantin-yang-akan-ledakkan-bom-di-bali.
 V. Arianti and Nur Azlin Yasin, “Women’s Proactive Roles in Jihadism in Southeast Asia,” Counter Terrorist Trends and Analyses Vol. 8, No. 5 (May 2016), p. 10, https://www.rsis.edu.sg/wp-content/uploads/2016/05/CTTA-May-2016.pdf.
 Institute for the Policy Analysis of Conflict, “Mothers to Bombers.”
 Unaesah Rahmah, “Women in Jihad: An Indonesian Context,” Counter Terrorist Trends and Analyses Vol. 12, No. 4 (June 2020), pp. 21-26, https://www.rsis.edu.sg/wp-content/uploads/2020/06/CTTA-June-2020.pdf.
 “Mothers to Bombers: The Evolution of Indonesian Women Extremists,” IPAC Report No.35.
 Wahyudi Soeriaatmadja, “Women Migrant Workers Vulnerable to Online Radicalisation, Says Jakarta-Based Think-Tank IPAC,” The Straits Times, July 26, 2017, https://www.straitstimes.com/asia/se-asia/women-migrant-workers-vulnerable-to-online-radicalisation-says-jakarta-based-think-tank.
 Bobby Chandra, “Anak Imam Samudra Tewas Di Suriah, Ini Kata Kapolri,” Tempo, October 26, 2015, https://nasional.tempo.co/read/713162/anak-imam-samudra-tewas-di-suriah-ini-kata-kapolri.
 Farhan Yurisa Ghea, “Kisah Tragis Tewasnya Anak Brekele Di Suriah,” Detik News, September 14, 2017, https://news.detik.com/x/detail/investigasi/20170914/Kisah-Tragis-Tewasnya-Hatf-di-Suriah/.
 Anthrax is a rare infectious disease caused by the bacterium Bacillus anthracis. There are three forms of anthrax infection: cutaneous (skin), inhalation (lungs) and gastrointestinal (stomach and intestine). Anthrax can lead to multiple organ failure, massive bleeding and eventually death.
 “Yazid Sufaat,” United Nations Security Council, May 21, 2009, https://www.un.org/securitycouncil/sanctions/1267/aq_sanctions_list/summaries/individual/yazid-sufaat.
 Simon Elegant, “Untangling The Web,” TIME, February 4, 2001, https://content.time.com/time/subscriber/article/0,33009,197713,00.html.
 Rueben Ananthan Santhana Dass, “Jihadists’ Use and Pursuit of Weapons of Mass Destruction: A Comparative Study of Al-Qaeda and Islamic State’s Chemical, Biological, Radiological and Nuclear (CBRN) Weapons Programs,” Studies in Conflict & Terrorism, October 27, 2021, pp. 1-35, https://doi.org/10.1080/1057610X.2021.1981203.
 Abdul Nasir, “Islamic State Militants in Malaysia and Indonesia Increasingly Using High-End Explosives.”
 V. Arianti, “Biological Terrorism in Indonesia,” The Diplomat, November 20, 2019, https://thediplomat.com/2019/11/biological-terrorism-in-indonesia/.
 “Factory Worker Jailed for Terrorism-Related Crimes,” The Star, May 12, 2017, https://www.thestar.com.my/news/nation/2017/05/12/factory-worker-jailed-for-terrorismrelated-crimes.
 Raffy Tima, “Marawi, The Drone War,” GMA News Online, November 11, 2017, https://www.gmanetwork.com/news/topstories/specialreports/632793/marawi-the-drone-war/story/.
 Kenneth Yeo, “As Southeast Asia Reopens, Will Transnational Terrorism Return?” The Diplomat, April 15, 2022, https://thediplomat.com/2022/04/as-southeast-asia-reopens-will-transnational-terrorism-return/.
 “Bom Panci di Bekasi Berdaya Ledak Tinggi, Ini Bahan Bakunya,” Tempo, December 15, 2016, https://nasional.tempo.co/read/828149/bom-panci-di-bekasi-berdaya-ledak-tinggi-ini-bahan-bakunya.
 Abdul Nasir, “Islamic State Militants in Malaysia and Indonesia Increasingly Using High-End Explosives.”
 Rina Chadijah, “300 Kg Bahan Pembuat Bom Disita Dari Rumah Terduga Teroris di Sibolga,” Benar News, March 14, 2019, https://www.benarnews.org/indonesian/berita/bahan-peledak-teroris-sibolga-03142019142325.html.
 Andi Saputra, “Perakit Bom di Batang Divonis 5 Tahun Penjara,” Detik News, July 1, 2021, https://news.detik.com/berita/d-5627381/perakit-bom-di-batang-divonis-5-tahun-penjara.
 V. Arianti and Unaesah Rahmah, “Annual Threat Assessment: Indonesia,” Counter Terrorist Trends and Analyses Vol. 14, No. 1 (January 2022), pp. 11-20, https://www.rsis.edu.sg/wp-content/uploads/2022/01/CTTA-January-2022.pdf; Abu Hamzah was another bomb supplier, but he failed to carry out his planned attacks as he was arrested along with another suspected JAD member from Lampung, Rinto Sugianto alias Putra Syuhada. Abu Hamzah, Rinto and three women had planned to carry out coordinated suicide bombings at police stations in Sibolga using the bombs made by Abu Hamzah.
 Unaesah Rahmah, “Annual Threat Assessment: Indonesia,” Counter Terrorist Trends and Analyses Vol. 13, No. 1 (January 2021), pp. 14-21, https://www.rsis.edu.sg/wp-content/uploads/2021/01/CTTA-January-2021.pdf.
 Machetes are used for agricultural activities, clearing tall grass and cracking coconuts in some parts of Indonesia and the Philippines. Hence, a machete is considered a necessary household item and its supply chain is unregulated.
 Rahmah, “More Terrorists are Using Guns in Indonesia.”
 While some may argue that a “sin tax” creates shadow economies, the Philippines already has a shadow economy for guns and ammunition despite the absence of an ammunition tax. The implementation of an ammunition tax would increase the cost of ammunition in the legal arms market and, theoretically, also in illicit markets. See Tatsuo Hatta and John Haltiwanger, “Tax Reform and Strong Substitutes,” International Economic Review Vol. 27, No. 2 (June 1986), pp. 303-315, https://www.jstor.org/stable/2526506.
 Arianti and Rahmah, “Annual Threat Assessment: Indonesia,”; Rahmah, “Annual Threat Assessment: Indonesia.”
 Roel Pareño, “Abu Sayyaf ‘Bomb Courier’ Killed in Basilan,” The Philippine Star, July 1, 2022, https://www.philstar.com/nation/2022/07/01/2192105/abu-sayyaf-bomb-courier-killed-basilan.
 Kenneth Yeo, “The Strategic Patience of Dawlah Islamiyah in Mindanao,” The Diplomat, March 21, 2022, https://thediplomat.com/2022/03/the-strategic-patience-of-dawlah-islamiyah-in-mindanao/.
 Azhar Bagus Ramadhan, “7 Terduga Teroris yang Ditangkap di Gorontalo Berencana Serang Markas Polisi,” Detik News, February 4, 2021, https://news.detik.com/berita/d-5361332/7-terduga-teroris-yang-ditangkap-di-gorontalo-berencana-serang-markas-polisi.
 Azhar Bagas Ramadhan, “Densus 88 Ungkap Peran 3 Tersangka Teroris yang Ditangkap di Bima,” Detik News, June 21, 2022, https://news.detik.com/berita/d-6138190/densus-88-ungkap-peran-3-tersangka-teroris-yang-ditangkap-di-bima.
 Organization for Security and Co-operation in Europe (OSCE), Women and Terrorist Radicalization: Final Report (Vienna: OSCE, February 2013), https://www.osce.org/files/f/documents/4/a/99919.pdf.