September17, 2008:  Despite all the bad press it gets, "electronic walls" have reached the point where you can bet your life on them. The U.S. was the first to employ these systems on a wide scale, during the Vietnam war. The most successful aspect of this was the dropping of acoustic sensors deep into enemy territory. These provided useful information about what was going on in there. As the sensors got better, the uses of "electronic walls" became more ambitious. Israel has used them as part of their security system around Gaza. It has been quite successful there, but the only time you hear about the Israeli system is when it fails. But that's what all such systems are prone to do from time to time, and that's the only time the media will pay much attention.

The basic problem with the use of electronic walls is that a determined enemy can, under the right conditions, figure out how to fool the system and get through. Well, some of the time, anyway. The classic penetration method is to first carefully examine as much of the system as you can, and then gain more knowledge by having some of your people try to get through it. Each of these attempts will try to exploit another actual, or induced, weakness in the system, until you have figured out how to get past all the sensors (usually a combination of acoustic, seismic and visual one, along with physical barriers). This cannot be done, or at least it's extremely difficult, where the barrier is covered with lethal fire. That is, anyone who tries to get through and is detected, gets killed. That limits the effectiveness of these trial runs, not to mention making it difficult to recruit people for this kind of work. Israel used lethal firce on the Gaza barrier, and the U.S. used that for its electronic walls around its bases in Iraq and Afghanistan. India has used such sensors to make it more difficult, or at least more costly, for Islamic terrorists to sneak into Kashmir (using the remote, and forested, mountains that comprise much of the border.)

Nevertheless, these barriers are also being widely used, in non-lethal mode, to protect national borders in Iraq, Jordan, Saudi Arabia, Israel and the United States (along the Mexican border.) There are ways to make non-lethal barriers more difficult to penetrate, but it costs more money. It all depends on how much you want to spend.

Meanwhile, the trend is towards more sensitive, cheaper and rugged sensors. The software used to interpret the sensor data also becomes more powerful. This makes it more difficult to fool the sensors. Moreover, the sensors can be moved around periodically, or used in different combinations, to further complicate the task of anyone trying to figure out how to get through.