KaPo annual review 2016 discusses cyber security on page 21:

In 2016, Estonia also saw some attempts to access the information of the state’s high-level decision-makers. The attacks were extremely skilfully executed from the technical point of view with the use of credible fake e-mails and previously unknown technical methods. In view of the functioning mechanisms of the abovementioned APTs, it is clear that attacks cannot be avoided entirely, but they need to be identified, and major damage needs to be mitigated.
[..]
As far as Estonia is concerned, we forecast that cyber threats will increase in 2017 due to the EU presidency and the arrival of NATO units.

The section “Protection of state secrets” covers the case of Alexander Goncharov and Ivo Jurak on which we reported before.

Links:
https://kapo.ee/sites/default/files/public/content_page/Annual%20Review%202016.pdf