"Just as when countering cyber-attacks from Russia in 2007, private companies, NGOs and the free press have been able, in cooperation with national authorities, to expose attempts made on social media to distort information and influence the public through fake NGOs, spreading lies and inciting disagreement," Mr Sinisalu writes.

Five years after the illegal annexation of Crimea, the approach Russia has taken is "plain to anyone who wants to understand it," he adds: "Russia does with its neighbours whatever it can get away with."

In terms of how the Western countries, the EU and NATO respond to its actions, one should keep in mind that history knows no positive examples of making concessions to dictators and autocrats. Case in point: the Munich Agreement, or also the Molotov-Ribbentrop pact with its secret protocol that divided Europe and had disastrous consequences for Estonia.

The aftershocks of history, meanwhile, continue in Russia's present-day behaviour. "It is often thought that Kremlin propaganda is less of a threat in Estonia than it is elsewhere in Europe. I cannot entirely share this optimism," Mr Sinisalu adds. There is an "unpleasant and thought-provoking" aspect to the current situation, especially where last year's treason cases are concerned.

"Treason undermines and threatens both the rights and freedoms guaranteed by our Constitution and, indirectly, Estonia's independence itself. Traitors are never easy to catch," Mr Sinisalu writes.

According to the ISS' annual review, Estonia's security authorities since 2006 have apprehended, tried and convicted six individuals for treason, and another 12 were sentenced for committing crimes against the state by collaborating with Russian special services.