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Potential Indicators of Threats Involving Vehicle Borne Improvised Explosive Devices

The following information is meant to advise the public as well as people who own and operate facilities about possible indicators of terrorist attack planning.

DHS encourages individuals to report information concerning suspicious or potential criminal activity to law enforcement or a Homeland Security watch office. Individuals also may report incidents to the Homeland Security Center (HSC) at 202-282-1616, email to

The Department of Homeland Security believes that a truck bombing by terrorists may be preempted if the general public remains alert for certain indicators.

DHS has no specific information to indicate that a truck bombing of any kind is currently being planned in the United States.

This document is only intended to provide general information to assist in efforts to recognize potential VBIED-related threats or incidents based on the recent Riyadh bombings.

Current Tactics Used in the Riyadh Attack

  • Multiple targets
  • Simultaneous attacks
  • Multiple vehicles per target
  • Assault/breaching cadre armed with small arms/weaponry accompany the VBIED to clear security personnel and gain access to the compound.

International terrorist groups have demonstrated the ability to plan and conduct complex attacks, simultaneously, against multiple targets. In the 11 May Riyadh attack terrorists, possibly Al-Qaida, assaulted three compounds occupied by western guest workers using multiple vehicles.

At least one vehicle in each assault team carried a large explosive charge which was detonated by a suicide bomber.

Media reports indicate that the attackers drove up to each compound killing those guarding the compound gates with small arms fire. Vehicles carrying the explosive charges were then driven into each compound and detonated.

In one instance it appears that the terrorists attempted to breach the gate security check point by ramming it with a sedan. It is likely that those involved with executing these attacks conducted extensive preoperational surveillance of the compounds selected.

Meticulous planning, to include preoperational surveillance, is a hallmark of Al-Qaida terrorist attacks.


  • Sustained the least amount of damage of the three targets. Initial attack penetrated one Saudi Military Guard manning watch post at rear corner of compound.
  • Assailants killed the guard and drove the explosive laden car up to the next gate in the back of the compound, where it was detonated.
    - Of note, a safe house probably used by these terrorists -- which was raided by Saudi authorities on 6 May -- was only 400 meters from the Jedawal Compound.


  • This compound was located on a Saudi National Guard (SANG) controlled facility.
  • Initial attack was conducted with a Ford Crown Victoria sedan, which attempted to ram through the gate of the compound.
  • When the car became stuck, terrorists from a pick-up truck dismounted and attacked the guard post.
  • Firefight ensued, killing all SANG personnel.
  • Terrorists forced open the gate, and drove the pick-up on the compound.
  • Truck was driven up to residence housing, where it was detonated (initial estimate suggests 400-500 kilograms of High Explosives (HE) may have been used).


  • Toyota sedan pulled up to the gate, followed by a GMC Suburban truck.
  • An unknown number of terrorists dismounted from the truck, shot and injured an unarmed guard, and forced their way into the compound.
  • Both vehicles drove toward the center of the compound where the terrorists shot into buildings and at moving objects.
  • Upon reaching a housing area south of the main recreation and sports complex, an explosive device in the GMC Suburban was detonated by a suicide terrorist.

While the ability to conduct multiple, near simultaneous attacks against several targets is not new for terrorist groups such as Al-Qaida, the manner in which these attacks was conducted indicates a more refined capability.

In each attack a number of armed terrorists was used to eliminate the security elements guarding the compounds so suicide cadre could drive a vehicle borne improvised explosive device to the desired location and detonate it.

Media reports suggest that the terrorist perpetrators may also have fired shots in the air to lure victims out of their dwellings in order to maximize casualties. The split second timing among the reported three attacks -- while not unprecedented for accomplished terrorist groups - indicates that a trained and dedicated cadre perpetrated this attack.

Potential VBIED Indicators

DHS has no specific information to indicate that a truck bombing of any kind is currently being planned in the United States.

The existence of any one of the following indicators does not in and of itself suggest terrorist activity. Each incident should be carefully assessed together with other information present to judge whether there is cause for further investigation:

  • Theft of explosives, blasting caps, or fuses, or certain chemicals used in the manufacture of explosives.
  • Rental of self-storage space for the purpose of storing chemicals or mixing apparatus.
  • Delivery of chemicals directly from the manufacturer to a self-storage facility or unusual deliveries of chemicals to residential or rural addresses.
  • Chemical fires, toxic odors, brightly colored stains, or rusted metal fixtures in apartments, hotel/motel rooms, or self-storage units.
  • Modification of truck or van with heavy duty springs to handle heavier loads.
  • Small test explosions in rural wooded areas.
  • Treatment of chemical burns or missing hands/fingers.
  • Untreated chemical burns or missing hands/fingers.

Purchase or theft of explosives or chemicals may be a precursor to terrorist attacks -Ramsi Yousef--the mastermind behind the 1993 World Trade Center (WTC) attack--purchased the required chemicals directly from a chemical manufacturer.

Timothy McVeigh--the perpetrator of the attack on the Murrah Federal Building--used a combination of theft and small purchases over a six (6) week period to amass the necessary ingredients used to assemble his explosive device.

Rental of self-storage units and the delivery of chemicals to such units - Both Ramsi Yousef and Timothy McVeigh rented self-storage units in order to store chemicals. Ramsi Yousef had the chemical manufacturer deliver $3,400 in chemicals directly to his self-storage unit.

Chemical fires, toxic odors, brightly colored stains, or rusted metal fixtures in apartments, hotels rooms, or self-storage units - Self-storage site managers, motel/hotel staff, and apartment superintendents may wish to be sensitive to any fires, toxic odors, bright stains, or rusted metal fixtures within their facilities. In attempting to prepare an improvised explosive device in the Philippines following the 1993 WTC attack, Ramsi Yousef caused a violent chemical fire to break out in the kitchen where he was preparing his device.

Subsequent investigation of this apartment revealed bright stains and rusted metal fixtures (i.e., door hinges, window locks, etc.) throughout the apartment.

Theft of truck or van with minimum one (1) ton carrying capacity - The 1993 WTC attack and 1995 bombing of the Murrah Federal Building were carried out with rented vehicles.

However, terrorists may use a stolen vehicle in order to impede subsequent investigation. Moreover, most VBIEDs used in recent years have carried large explosive charge that weighed in excess of 2,000 pounds suggesting that continued use of large vans, SUVs or trucks for this purpose is likely.

Modification of smaller capacity vehicles to accept a minimum one (1) ton load - The two vehicles used in the 1998 East Africa bombings were imported into the target country and then locally modified with heavier springs in order to accommodate the weight of the explosive.

Local law enforcement may wish to coordinate with appropriate garages or auto mechanic trade associations in their jurisdictions to sensitize them to this indicator.

Small test explosions in rural or wooded areas - Timothy McVeigh detonated at least one small explosive device in a wooded area near his residence in order to test his chemical mixture. Local law enforcement, as well as fire and rescue departments, may be in the best position to report this indicator to the FBI.

Treated/untreated chemical burns or missing hands and/or fingers - Terrorists may seriously injure themselves while manufacturing their bomb that they require immediate and substantial medical care. Hospitals and out-patient clinics should therefore be requested to report such injuries.

Physical surveillance - Nearly every major terrorist attack is preceded by a thorough surveillance of the targeted facility. It is likely that similar activity preceded the Riyadh compound bombings.

Purchase of, or illicit access to, blue prints of the targeted facility - In a failed 1996 attempt to destroy the FBI’s fingerprint facility in Clarksburg, WV, a domestic anti-government group attempted to acquire the facility’s blue prints from a local emergency services worker. Receiving offices may wish to sensitize local fire and rescue departments, and architectural firms, to the possibility that terrorists may attempt to acquire a targeted facility’s blue prints from local emergency services worker.

General Characteristics of Terrorist Surveillance:

Terrorist surveillance may be either fixed or mobile.

  • Fixed surveillance is done from a static position, possibly an adjacent building, business, or other facility. In fixed surveillance scenarios, terrorists may establish themselves in a public location over an extended period of time or choose disguises or occupations such as street vendors, tourists, repair or deliverymen, photographers or even demonstrators.
  • Mobile surveillance usually entails observing and following persons or individual human targets, although it can be conducted against non-mobile facilities (i.e. driving by an embassy to observe the building or compound). To enhance mobile surveillance, many terrorists have become more adept at progressive surveillance.
  • Progressive surveillance is a technique whereby the terrorist will follow a target for a short period of time from point A to point B, withdraw for a time, possibly days or even weeks, and then resume surveillance from point B to point C. This will continue until the terrorist develops target suitability and/or noticeable patterns in the targets movements. This type of transient presence makes the surveillance much more difficult to detect or predict.
  • More sophisticated surveillance is likely to be accomplished over a long period of time. This tends to disrupt detection techniques and improve the quality of gathered information. Some terrorists are noted to perform surveillance of a target or target area over a period of months or even years.
  • Terrorists are known to use advances in technology such as modern optoelectronics, communications equipment, video cameras, and other electronic equipment. Such advances include commercial and military night-vision devices, GPS systems, and cellular phones. It should be assumed that many terrorists have access to high-dollar technological equipment.

Protective Measures Terrorists continue to select soft targets for attack -- particularly those that will yield a high casualty count. Some examples, though not all inclusive, are: residences, recreational and shopping venues, and business buildings and complexes. All available antiterrorism measures should be rigorously reexamined - to include: physical security perimeters set back distances between security fences and key buildings, and barricades.

  • Maintain situational awareness of world events and ongoing threats.
  • Ensure all levels of personnel are notified via briefings, email, voice mail and signage of any changes in threat conditions and protective measures.
  • Encourage personnel to be alert and immediately report any situation that appear to constitute a threat or suspicious activity.
  • Encourage personnel to avoid routines, vary times and routes, pre-plan, and keep a low profile, especially during periods of high threat.
  • Encourage personnel to take notice and report suspicious packages, devices, unattended briefcases, or other unusual materials immediately; inform them not to handle or attempt to move any such object.
  • Encourage personnel to keep their family members and supervisors apprised of their whereabouts.
  • Encourage personnel to know emergency exits and stairwells and the locations of rally points to ensure the safe egress of all employees.
  • Increase the number of visible security personnel wherever possible.
  • Rearrange exterior vehicle barriers, traffic cones, and road blocks to alter traffic patterns near facilities and cover by alert security forces.
  • Institute/increase vehicle, foot and roving security patrols varying in size, timing and routes.
  • Implement random security guard shift changes.
  • Arrange for law enforcement vehicles to be parked randomly near entrances and exits.
  • Review current contingency plans and, if not already in place, develop and implement procedures for receiving and acting on threat information, alert notification procedures, terrorist incident response procedures, evacuation procedures, bomb threat procedures, hostage and barricade procedures, chemical, biological, radiological and nuclear (CBRN) procedures, consequence and crisis management procedures, accountability procedures, and media procedures.
  • When the aforementioned plans and procedures have been implemented, conduct internal training exercises and invite local emergency responders (fire, rescue, medical and bomb squads) to participate in joint exercises.
  • Coordinate and establish partnerships with local authorities to develop intelligence and information sharing relationships.
  • Place personnel on standby for contingency planning.
  • Limit the number of access points and strictly enforce access control procedures.
  • Approach all illegally parked vehicles in and around facilities, question drivers and direct them to move immediately, if owner can not be identified, have vehicle towed by law enforcement.
  • Consider installing telephone caller I.D., record phone calls, if necessary.
  • Increase perimeter lighting.
  • Deploy visible security cameras and motion sensors.
  • Remove vegetation in and around perimeters, maintain regularly.
  • Institute a robust vehicle inspection program to include checking under the undercarriage of vehicles, under the hood, and in the trunk. Provide vehicle inspection training to security personnel.
  • Deploy explosive detection devices and explosive detection canine teams.
  • Conduct vulnerability studies focusing on physical security, structural engineering, infrastructure engineering, power, water, and air infiltration, if feasible.
  • Initiate a system to enhance mail and package screening procedures (both announced and unannounced).
  • Install special locking devices on manhole covers in and around facilities.

Note: Substances and Amounts compiled from publicly available sources.

Prepared by: Risk Assessment Division, Information Analysis Directorate, Department of Homeland Security.