[7][9][10][11] According to a 2017 exposé by the Finnish newspaper Helsingin Sanomat, the Finnish Intelligence Research Centre is responsible for monitoring the Russian Armed Forces by capturing and analysing electromagnetic radiation and maintaining an electronic intelligence mapping that contains information on the Russian military, such as unit types, command and control structures, air defences, readiness plans and missions.

[6][11] During procurement, the CASA was required to be able to monitor signals from 1,5 MHz to 40 GHz, listen to a minimum of a hundred different channels, and be NATO compatible to fulfil its intended mission.

By 1934, the Office could intercept and decrypt Soviet Navy messages after monitoring and comparing its communications and movement extensively with a Hansa-Brandenburg W.33 reconnaissance plane above the Gulf of Finland and from neighbouring islands.

[14][15][17][18][19] As the Winter War began in 1939, Hallamaa and the SIGINT assets under his command were reorganized as the Signals Intelligence Office (Finnish: Viestitiedustelutoimisto).

[16] The Signals Intelligence Office was able to intercept Soviet messages and inform Colonel Hjalmar Siilasvuo of Red Army movements during the Battle of Suomussalmi.

the Finns intercepted messages guiding the encircled Soviet troops how to light up signal fires for air supply pilots to recognize during night-time.

[14][18][20][21] During the Interim Peace in 1940, Hallamaa traded broken Soviet ciphers with other states to fund Finnish signals intelligence operations—for example to the Swedes in exchange for RCA transmitters.

Finnish intelligence also made mistakes by revealing too much of its knowledge, such as in 1941 when eager personnel messaged the Red Fleet with its own ciphers to surrender.

Subsequently, the 50,000 Finnish defenders was able to halt the 150,000 men in the Soviet attack and the Vyborg-Petrozavodsk Offensive, the last big operation of the Continuation War.

[14] In the autumn of 1944, after the Moscow Armistice, 700 to 800 Finnish SIGINT staff fled to Sweden with 350 crates of cryptography equipment in operation Stella Polaris, led by colonels Aladár Paasonen and Reino Hallamaa.

C-byrån of the Swedish military and the National Defence Radio Establishment coordinated the operation at their end and received, for example, cracked ciphers from the Finns.

Some war-time documents hidden in the operation were later reportedly found in microfilms, for example, at the CIA's central archives and NSA's National Cryptologic Museum—while some have not resurfaced.

[4][10] In December 2017, the newspaper Helsingin Sanomat wrote an exposé about the Intelligence Research Centre based on leaked classified Defence Forces' documents.

[7] President of Finland Sauli Niinistö issued a statement where he deemed the leak illegal and critical to national security, and a criminal investigation was initiated.

The responsibilities of the Topography Section (Finnish: Topografikunta) of Defence Command and the Surveying Battery overlapped during the 1920s and 1930s and the units disagreed on whether to centralize or decentralize GEOINT assets.

[23] The barrage was considered a world record of artillery at the time and according to Nenye and others, halted and destroyed over thirty Soviet formations larger than a battalion.