Clive Robinson • September 30, 2008 9:22 PM

@ Steve, Nick Lancaster,

One thought occurs to me and that’s “resource scarcity”.

Bomb squad officers are not exactly “thick on the ground”. And unfortunatly probably do have a lot of calls on their time.

If you bring a “time window” into the equation then as a practical response why bother investigating the device?

It would be more sensible to make an assessment based on physical size and package placment and act according to “the book”.

This does tend to gives rise to a process of “if you only have a hammer then everything gets treated as a nail” but it importantly it’s consistant.

Further If you think about the types of “real” devicess they occasionaly come across investigation is not something you want to be making. Because time is never going to be on your side.

A sensible stratagy is “break it then investigate”. That is disruptive deactivation works almost every time, and importantly it effectivly “stops the clock”. This gives the investigators plenty of time to safely check the bits whilst the bomb squad move on to the next incident.

I would say it was a sensible response to a time critical situation based on current evidence.

After all it’s very much what all emergancy responders actually do be it a fire, a serious accident or crime in progress, “assess, respond and then investigate”.

We are only talking about this because the first two steps for a bomb threat appear so dramatic and due to the scarcity of real devices it appears to be overkill.

But is it overkill?

It depends first on your time and distance equation for safety, and what your safety criteria are.

Then on the available resources you have available at the time.

And that’s the crunch due to “resource scarcity” you will have to optomise a process. Which is why you have first / second / third “responders”, “technical support”, etc.

Then there is the question of “drill” in an emergancy you do not know at what point people will become “overwhelmed” and cease to act rationaly. Their threshold goes up considerably with training and removale of decision making.

A practical example is learning to drive a car your driving instructor tells you simple “mantras” over and over again untill they become subconciously automatic, when they do they take you to the next stage and so on. We even joke about it with “you know the drill” or “by the book”.

It quite effectivly takes the unknown human out of the equation and replaces them with a known quantity, which people further up the chain of command can usually count on (which is very important).

Finally there is the question of cost, of which manpower and training are generally the ones accountants worry about.

Therefor it is probably less costly to actualy do a quick assesment, send in a robot with a shotgun or small explosive package to disruptivly deactivate the device, packup and move onto the next one.

The ultimate question is at what point do you reassess the the “book” and the attendant “drill”. The first is when it is seen not to be effective, the second is when the cost is disproportianate. They are both based on assumptions and risk, change either and the rest follows. The problem with low probability events is that usually our assumptions are wrong and there is insufficient data to calculate risk.

Clive Robinson • October 1, 2008 4:27 AM

@ Jon Sowden,

“… and 666 for IEDs.”

Ah the mark of the Devil.

On a more serious note. Most IEDs employed in civilian areas in the WASP Nations are thankfully not designed by people who know what they are doing.

If you remove the experiments of children and adolescents (including thermite mountins for science projects that go wrong). And other oddities like home beer making that has gone badly wrong. You are left with the devices that are deliberatly designed to cause harm.

In the U.S. from what little published information exists IEDs predominantly have specific targets and are often put in the targets car. The bomb of choice appears to be a steel pipe with a low explosive (ie that bought for refilling amunition). Effectivly a bigger and much nastier version of a home made firework.

The pipe acts as the tamper casing to improve yeild and provide shrapnell. It would appear that the usuall mistake made is to overfill the pipe which tends to cause it to burst not fragment and as a conciquence gives a much lower yield than would otherwise result from a more knowledgable designer.

This over fill issue has been known for several hundred years. Guido Fawks of the gunpowder plot knew that the barrels the gunpowder was put in should only be about 1/3 filled with gun powder to get the best yield.

It was anomalies seen in explosives testing and knowledge of the yield issues that led to research in the mid 1900’s which gave rise to shaped charges which are used both militarily and comercialy.

It would appear that in quite a few conflict zones this knowledge is known by the builders of IEDs with the result they are considerably more effective.

This has a conciquence in that when constrained by a substantial tamper casing disruptive deactivation of an IED becomes less of an option unless the trigger mechanisum is external to the tamper casing, in which case the trigger mechanisum gets the shotgun treatment.

Clive Robinson • October 2, 2008 1:44 AM

@ DavidHeath,

“… carry-on bag with a trigger-mechanism based on high levels of X-rays!”

The scanners are supposadly “film safe” these days which sugests the level of X-rays is a lot lower than it once was so your triger could go off if for instance it got to close to an older terminal with a CRT in checkin…