Indonesian police arrested six men in Batam on Aug. 5 who they claim were planning to fire a rocket at Singapore under the direction of a known Islamic State member. Part of Indonesia's Riau Islands province, Batam is about 16 kilometers (10 miles) across the Singapore Strait from Singapore, to which it is linked by ferry service. The island is a popular getaway for Singaporeans who want to golf or to visit its beach resorts. It also plays host to many factories owned by electronics firms, which employed the six arrestees (one of whom has been released).

Initial reports suggest that the group had been in communication with Bahrun Naim, an Indonesian Islamic State leader located in Syria who has been encouraging jihadists in Indonesia to conduct attacks in their home region. Naim is believed responsible for planning the Jan. 14 bombing and armed assault at the Sarinah shopping center in Jakarta. He is also suspected of planning the botched July 4 suicide bombing against a police office in Surakarta in Central Java, an attack that wounded a police officer.

Naim has struggled to impart terrorist expertise from his organization in Syria to jihadists in Indonesia. For example, the Sarinah shopping mall was crowded with shoppers when that attack took place, yet only four people were killed. The attackers struggled with poor bombmaking and operational skills: Two of the bombers managed to blow themselves up while lighting one of their primitive pipe bombs.

So in spite of media reports that the group in Batam was plotting a rocket attack, the attackers were very likely incapable of much beyond simple attacks involving small arms or pipe bombs. Police reportedly recovered bombmaking materials, guns and arrows during searches of the suspects' homes — not rockets or rocket-making materials. Apparently, the group was more aspirational than operational, something not uncommon with Indonesian jihadists ever since Indonesian authorities managed to arrest or kill the last cohort of terrorist planners with the tradecraft required for large attacks, such as the October 2002 Bali bombing.

Any attack launched by the Batam group probably would have been a simple attack against a soft target, such as one of the resorts in Batam — or the electronics factories where they worked. The jihadists' employment at electronics factories once more highlights the insider threat from grassroots jihadists.

Insider Threats

Corporate security officers rightly fear the threat of terrorist attacks perpetrated in the workplace by grassroots jihadists, such as one in June 2015 by Yassin Salhi, a truck driver in Lyon, France, working for the U.S.-owned Air Products. Salhi decapitated his manager before ramming a vehicle into the factory in what he told police was an attempt to cause a massive explosion.

The December 2015 armed assault in San Bernardino, California, is another example of such an attack. In that incident, Syed Rizwan Farook returned to work with his wife, Tashfeen Malik, after an altercation at his office holiday party, gunning down his co-workers and trying to detonate a bomb. They killed 14 people and wounded another 21 before dying in a shootout with police.

Though the San Bernardino attack differs from many incidents of workplace violence in that it involved two shooters instead of the usual lone attacker, we have seen similar insider attacks involving multiple hostile actors abroad. For example, three of the gunmen involved in the May 2004 armed assault against ABB Lummus Global's petrochemical facility in Yanbu, Saudi Arabia, worked there. Their security badges and familiarity with the layout of the facility were key to launching the attack.

Even when insiders do not mount the attack themselves, they can provide crucial inside information that can greatly assist those planning an attack. The January 2013 assault against the Tigantourine natural gas facility near Ain Amenas, Algeria, which reportedly involved more than 30 attackers, appears to have relied on information from inside regarding the plant's layout and transportation arrangements for expatriate employees.

Insiders can also slip weapons past security. An employee of a florist with stores in the JW Marriott and Radisson hotels in Jakarta smuggled bombs inside that were later used in the July 2009 suicide attacks against them.

Insiders can pose another threat: using company resources to facilitate attacks elsewhere. Nidal Ayyad, a chemical engineer with AlliedSignal, used company letterhead to place orders for the large quantities of chemicals needed to manufacture the explosives for the truck bomb used to attack the World Trade Center in 1993. Obtaining large quantities of those industrial chemicals would have been difficult without his assistance. Insiders also could use their access to industrial chemical facilities to release dangerous chemicals in an attempt to create a mass casualty attack.

Countering the Insider Threat

In many ways, the sort of grassroots jihadist-related workplace violence seen in Lyon and San Bernardino is similar to workplace violence conducted by attackers not motivated by jihadism. Psychological problems do not preclude ideological motivations; both can play a role in insider attacks involving grassroots jihadists. This confluence was seen in the November 2009 Fort Hood shooting. The shooter, Maj. Nidal Malik Hasan, had become radicalized and was in communication with al Qaeda leader Anwar al-Awlaki. But he had also exhibited alarming behavior inside and outside the workplace, revealing a deteriorating mental state.

It is exceedingly rare for a case of workplace violence (jihadist or otherwise) to happen without the shooter conveying warning signs of the impending attack. Investigators frequently find that such warning signs were either downplayed or simply ignored. After the Fort Hood attack, it emerged that numerous complaints and warnings about Hasan's strange and menacing behavior went unheeded.

Warning signs that an employee or former employee could be capable of workplace violence can include sudden changes in behavior, decreased productivity, uncharacteristic problems with tardiness and attendance, or withdrawal from social circles. The theft or sabotage of employer or co-worker property is another sign, as is the sudden display of negative traits, such as unusual levels of irritation, snapping at or abusing co-workers, or a sudden disregard for personal hygiene.

Probably the most telling signs of impending violence are talk about suicide or martyrdom and issuing direct or veiled threats against others. Another significant warning sign noted prior to several workplace violence incidents are co-workers' or supervisors' fears of a person, even when no reason for these fears can be articulated.

In many companies, countering workplace violence is often thought to be the corporate security department's problem. Nothing could be further from the truth. Most corporate security departments are bare-bones operations and are quite often the first to undergo cuts when companies face tough economic times. Most corporate security departments focus on physical security, loss prevention and theft of company property. With their limited staff and large responsibilities, they have few opportunities to learn what is going on with the guy in that middle cubicle on the third floor who watches a lot of jihadist propaganda and has become angry at the West. Even companies with teams dedicated to protecting senior company officials often largely focus on the outside threat. Those personnel pay far more attention to protecting the CEO during a trip abroad than during a walk through the company cafeteria. Senior company executives also often seem to believe that internal threats could not possibly exist in their company, an unsafe assumption at any firm.

Since police and corporate security departments are neither omnipresent nor omniscient, other people in the company must alert them to the potential for workplace violence. Co-workers and first-line managers generally are the first to notice warning signs, so the real first line of defense against insider threats must be a company's employees. Employees therefore must be educated about the insider jihadist threat in the same way they are about other workplace violence threats. They must also be encouraged to speak up about potential threats without the fear of retaliation. This empowerment comes from training and in the form of communication not only from the top down but also from the bottom up.

The company's top management must set the expectation that reports will be taken seriously. Human resources, corporate security and legal personnel must have a mandate to handle these cases early and quickly. The warnings provided by co-workers regarding Hasan were ignored because those who received them were not empowered or encouraged to take action. Instilling a culture of proactivity on potential insider threats may be challenging. This may be especially true at remote locations like a semiconductor factory in Indonesia, but doing so is every bit as important at such sites. The cost of ignoring the warning signs of an insider threat, no matter where it occurs, has often been tragedy.

This article originally appeared on Stratfor.com