The 2012 incident was the third time North Korea used GPS jamming against South Korea. For most of March 2011, North Korea directed GPS jamming signals across the border towards Seoul. A separate jammer targets mobile traffic. GPS jamming signals can be detected as far as one hundred kilometers south of the DMZ.
The usual response to GPS jamming is to bomb jammers, which are easy to find (jammers are nothing more than stronger versions of broadcasting the frequencies you want to jam). But such a response could lead to more fighting in South Korea, so there was no strong response to the southern protests. Jamming is more of an annoyance than a threat, and most military equipment comes with electronics and other upgrades to defeat it. The North Korean interference confirmed what was already suspected. Therefore, electronic warfare experts in South Korea and the United States have the opportunity to study the impact of jamming on metropolitan areas. This is causing intermittent issues for GPS device users as well as many other phone connection issues. Shorter, less powerful disturbance events occurred in August 2010 and December 2010.
Meanwhile, this is old news for the U.S. Department of Defense, which has been developing anti-GPS jamming technology since the late 1990s. For years, military aircraft have been outfitted with complex and expensive GPS receivers, even when they were blocked. There are several ways to block attempts to jam the GPS signal. While some of these methods are well known, others are categorical. No one has yet successfully used GPS jammers in combat, but the potential is there. Now, the North Koreans are fully demonstrating GPS jamming. Anti-jamming technology is becoming more and more complex. None of the major players (the US, Russia, China, Israel, and several other industrialized nations) actually speak, and for good reason. If you don't know what technology other people are using, you can't deal with it.
Both China and Russia sell GPS jammers. In 2007, China released a powerful vehicle-mounted GPS jamming system. These "GPS jamming vans" are designed to create a "bubble" of protection in the area where the van is located. In the year before the 2003 invasion of Iraq, Saddam is believed to have purchased a number of GPS jammers to counteract the American JDAM GPS smart bomb. It's no secret that JDAM has a backup INS, and Iraq's GPS jamming efforts had no significant impact on the 2003 campaign.
There are several ways to defeat GPS jamming, and knowing which method uses US GPS-guided weapons, it is easy to develop a way to jam "anti-jamming" GPS. The USAF is understandably reluctant to discuss what it is doing. Given the cost of calibrating all existing GPS weapons, it is more likely that anti-jamming GPS weapons will only be used on targets critical to GPS accuracy. For most targets, the accuracy provided by an inertial guidance system will do just fine. Also note that you can bomb GPS jammers with bombs equipped with a guidance system connected to a GPS jamming signal. For this reason, it is believed that any use of GPS jammer will involve dozens of jammers within each protected area. GPS jamming has no effect on more precise laser-guided bombs, and some countries buy smart bombs with lasers and GPS/INS systems. Most countries are researching anti-jamming technology in case more interference is encountered in the war.