TOPSHOT - A photo taken on September 18, 2024, in Beirut's southern suburbs shows the remains of ... [+]
At 3:450 pm local time in Lebanon on Tuesday, over 3,000 portable paging acquired by terrorist group Hezbollah simultaneously exploded. At least 12 people were killed, the BBC reported the Lebanese health minister said, and hundreds more seriously wounded, with the casualties including children. This event would seem outlandishly implausible in a techno thriller, but reality is not always plausible.
Nobody has claimed responsibility for the attack, but it is hard to see that it could have been carried out by anyone except the Israeli intelligence services, who have a track record of audacious and technologically-sophisticated long-range assassinations, such as the remote-control killing of Iranian nuclear scientist Mohsen Fakhrizadeh and the killing of terrorist Yehiyeh Ayash aka "The Engineer" with a booby-trapped cellphone containing explosive.
How was the attack in Lebanon carried out?
Fire In The BATLab
Early speculation focused on the idea that this was essentially a software hack which caused the pager batteries to overheat and explode.
A battery ignites during testing at BATLab
The batteries used in many mobile devices can be vulnerable to a condition known as thermal runaway. As the battery heats up during operation , it starts a chemical reaction within the battery cell which produces more heat. This in turn accelerates the reaction and within seconds a battery can reach 750 F / 400 C. At these temperatures the battery compounds break down, producing gases which expand and rupture the battery casing. The gases are typically organic solvents which are flammable and can be explosive.
There have been several high-profile accidents from such events, like the series of fires associated with Galaxy phones in 2016, a spate of burn injuries from e-cigarettes and a laptop which caught fire on a Lufthansa flight last year,
Fires from batteries usually only occur where cells are damaged or there are manufacturing flaws. Most batteries are inherently safe in normal usage. Sandia National Laboratories Battery Abuse Testing Laboratory (BATLab) carries out extensive testing on batteries from button-sized to units powering electric trucks, and the chemistry of thermal runaway is well understood.
It might be possible to design a battery which would overload on command, but this would produce fires rather than the blasts seen in Lebanon. CCTV videos of the attacks indicate they involved something more explosive.
Miniature Munitions At War
The suggestion is that Hezbollah were hit by a supply chain attack, in which explosive devices were inserted into the pagers either at the point of manufacture or during transit from the maker to the users. The AR-924 pagers used weighed just 3.3 ounces / 95 grams including battery so this would require an extremely small bomb.
BLU-43 Dragontooth, one of the smallest antipersonnel mines ever made
Some of the smallest anti-personnel explosive devices ever fielded were the U.S. BLU-43 ‘Dragontooth’ mines used in Vietnam. These asymmetric mines are about two inches across and resemble a maple seed. They were scattered from the air to make trails impassable. Each mine weighs less than ¾ ounce (20 grams) and is filled with 1/3 oz / (9 grams) of nitro-paraffin liquid explosive. It should be possible to incorporate a similar quantity of explosive into a pager bomb.
Dragontooth mines tended to injure rather than kill. The Russians have widely used their own version in Ukraine – the PFM
The U.S. deployed some even smaller air-dropped mines during the Vietnam conflict, delivered by the thousand in cluster bombs. Known as ‘Gravel mines’ or ‘Button bombs’ these were simply fabric pouches, some not much bigger than a postage stamp, filled with shock-sensitive explosive. The mines were stored in liquid which evaporated after they were dropped, activating the mines.
Gravel mines typically contained about 1/3 oz / (9 grams) of Lead azide/RDX explosive, and were not very effective, the USAF calling them “little more than a nuisance." One of their main functions was to act as a warning of the presence of a Viet Cong patrol when they set one off.
More recent U.S. research has developed extremely small and presumably effective micro-munitions for drone operations. This work is largely classified.
Pager Bombs
Blast alone is not an effective lethal mechanism. Anti-personnel weapons are generally packed with large amounts of shrapnel, as the flying metal causes far more serious injury than blast alone. The Vog-17 grenade, widely used as a drone bomb in Ukraine, weighs 12 ounces (350 grams) but only contains 1.2 ounces (35 grams) of explosive.
If the attackers were able to tailor the explosive device within the pager, it may have been positioned to use other pager components as shrapnel, making it more effective than the mines above. Given that the pager is designed to be worn on a belt clip with one side facing towards the wearer’s body, a directional explosive could be engineered; this would be far deadlier than the tiny size of the device would suggest. The hundreds of Hezbollah operatives reportedly seriously injured suggest the device was notably lethal for something so small.
This attack looks like a one-off — the follow-up explosions of bombs in walkie talkies the next day looks like a continuation, and would have come through the same compromised supply chain — and surely terrorists and others will now be highly aware of the risk of explosive devices concealed in portable electronics. But it is an impressive demonstration of a highly-targeted attack using a few pounds of explosive to strike literally thousands of opponents at once.
Medics collect blood donations in Beirut after pagers used by Hezbollah members exploded across ... [+]
Update 19th September: Further information about the pager bombs supports the idea that only a tiny amount of explosive was involved. While an early NY Times report suggested that “as little as one to two ounces of highly explosive material” was used, this would be far too much to fit in a fully functioning 3-ouce pager. The BBC quoted an anonymous expert who suggested that “the devices most likely contained 10-20 grams [0.3-0.7 ounces] of explosive materials” which again seems high.
The first reports from sources in contact with Hezbollah experts who had studied unexploded devices, quoted by PBS
A detailed NYT report on the attacks claims that the pager battery units were "laced with the explosive PETN." Including explosive inside the cell would make it very difficult to detect, but it would be harder to trigger without a direct connection to the processor. PETN is a military-grade explosive used for demolition and in munitions.
The small quantity of explosive was effective because of how the device was triggered. An error message prompted the user to look at the pager screen, it then exploded, typically causing hand and facial injuries. A large number of victims suffering damage to one or both eyes, from shrapnel from the screen and pager body.
"We’re talking about hands injured, severely injured fingers torn, I’ve heard some doctors say we need to perform amputation surgeries to remove hands, [and] ... they need to perform surgeries for eyes to remove them,” according to a journalist quoted by BBC Newsday.
Injuries would have been much less severe if the devices went off while they were being worn. The pager bomb attacks were carefully engineered to cause maximum injury with firework quantities of explosive. Expect to see more creative micro-munition attacks in future.
Update September 19th: A report in The Guardian quotes a Lebanese security source as saying "Mossad injected a board inside of the device that has explosive material." This contradicts the previous claim that the explosive was in the battery. having the explosive on or integrated into a circuit board would make it easier to detect but would make detonation control much simpler. A second source gives the amount of explosive involved as 3 grams (0.1 oz). Reports seem to be converging on a similar figure for the size of the charge.
