The Israeli domestic intelligence service (Shin Bet) revealed in February 2019 that they had broken up a Hamas terrorist network in the West Bank and East Jerusalem that had used a communication system based on code words or specific gestures made by news readers on the defunct (since December 2018) Hamas al Aqsa TV station in Gaza. Such techniques are nothing new but it takes some effort to discover their use. This signal system was one of several developed to assist in creating and sustaining a network of Hamas operatives in the West Bank and parts of Israel. Hamas invested a lot of time, effort and key Gaza based agents to create a terrorist network capable of carrying out attacks in Israel using Palestinians in the West Bank and East Jerusalem who have Israeli ID cards. A third of these Palestinians have such ID cards, which allow the holders to freely travel between the West Bank and East Jerusalem. Shin Bet had cooperation from the West Bank government (Fatah) which sees itself as the legitimate ruler of Gaza while Hamas seeks to take control of the West Bank any way it can. This rivalry means Hamas particularly values pro-Hamas Palestinians in the West Bank who have Israeli ID cards and puts a lot of effort into recruiting and developing them as operatives capable of planning and carrying out major terror attacks in Jerusalem or elsewhere in Israel (using the even smaller number of pro-Hamas Israeli Arabs.).
To make such a terror network survive and perform well Hamas needed some way to communicate with its West Bank agents quickly (in an emergency or any time-dependent situation) and without detection by the Israelis. This has been done, for a while, using the al Aqsa TV station in Gaza. Known mainly for its anti-Israel and anti-Semitic propaganda it was long known by the Israelis that there was a certain amount of communication to Hamas agents in Israel and the West Bank via al Aqsa but it wasn’t until late 2018 that Israel was able to knock al Aqsa off the air by using multiple airstrikes on an al Aqsa facilities in Gaza (including the mobile broadcasting equipment). That loss came at a time when Hamas was suffering a the sharp reduction in foreign aid which made it impossible to quickly pay for new equipment and get al Aqsa back on the air. Again Israel had help from Fatah which has become a very dedicated foe of Hamas (which has controlled Gaza 2006).
Al Aqsa went off the air at the end of 2018 because it said it was bankrupt. What was not mentioned was how the recent Israeli air strikes on Islamic terrorist targets in Gaza were much more comprehensive, as far as al Aqsa TV was concerned, than included in the past. Israeli smart bombs hit four major structures, including the seven story headquarters of the Al Aqsa TV station. That alone would cost about $5 million to replace. Israel had located other al Aqsa assets, like the truck mounted mobile TV broadcasting equipment, and bombed these as well. All these airstrikes (and over 150 others) were delivered over a few days in response to a major Hamas rocket attack. After the retaliatory airstrikes, Hamas accepted a ceasefire and a month later al Aqsa announced it was broke and unable to get back on the air any time soon. It was not public knowledge then that the loss of al Aqsa TV was also a major blow to Hamas terrorist operations in the West Bank and Jerusalem.
Hamas still has use of radio stations, which had been used heavily since World War II for sending messages to agents in enemy territory. But TV could more easily hide its secret messages by using a combination of visual cues and code words. Radio broadcasts are still used for intelligence work, especially the use of short wave “numbers stations” to broadcast long messages via a series of numbers broadcast at a certain time on a regular basis. In July 2016 North Korea activated, for the first time since 2000, a numbers station. This is a special radio station that uses a specific shortwave radio frequency that periodically (on pre-arranged dates and times) broadcasts sequences of numbers. These broadcasts often last a few minutes then that channel goes silent.
Numbers stations were a popular 20th century technique for sending secret messages to agents in foreign nations or combat zones. It began during World War I, with Morse code used instead of a spoken voice. Given the frequency used and the strength of the signal the audience for these new North Korean messages was apparently in South Korea, China or Japan. Analysis of the audio indicated that the North Koreans were using Cold War era Russian (Soviet) broadcast equipment. Apparently this gear was put in storage in 2000 and revived for the new broadcasts.
Since the Cold War ended a few nations still use numbers stations, most notably Cuba, China, Taiwan, Israel and, until 2000, North Korea. For nations with international Internet access (and this does not include North Korea) there are more effective Internet-based methods for sending secret messages. North Korea is known to have used these Internet-based methods so it is a mystery as to why they have revived their numbers station broadcasts. Then again it could just be another ploy to frighten their enemies (which is just about everyone, especially South Korea, the United States and Japan.) These three nations do not appear alarmed by the broadcasts, but that could be said for most North Korean threats.