An Introduction to SIGINT

Signals Intelligence or SIGINT is an intelligence-gathering technique, that enables the interception of any piece of information transmitted by communications systems, radars or other electronic devices. SIGINT is crucial as it allows for the delivery of critical information to decision-makers and military forces on matters of national security.


Historically, only governments had the financial and technological capacity to conduct SIGINT. In the context of WWII, information obtained through SIGINT played a key role. Through it, states not only gained a strategic advantage over their enemies, but they also were equipped with a preventive crisis management mechanism. An example of this is the decryption of the Enigma code. The successful interception of German communication traffic enabled the UK to obtain information that helped to locate German U-Boats and planned attacks on convoys of cargo ships. SIGINT helped the Allied forces gain an advantage against the Germans during the Battle of the Atlantic and the campaigns in North Africa.

Another instance took place during the Cold War. As part of Operation Ivy Bells, the US Navy installed wiretapping devices on Soviet underwater communication lines located in the Sea of Okhotsk. This allowed the US to obtain information about Soviet submarine missile technology and nuclear first-strike capabilities. Although operational and technical details of the program are still classified, intercepted messages provided strategic insights. This facilitated bilateral dialogue to limit nuclear weapons development and the subsequent adoption of the SALT II Treaty.

During the COVID-19 pandemic, SIGINT technologies have been adopted to protect public health and limit the spread of the virus. This has been achieved through the development of apps, where individuals give consent to share personal data and location, used to identify possible contacts with carriers of the virus. Around 50 countries have already promoted and endorsed COVID-19 tracing apps, including Germany, the Netherlands, and Australia.