The claim was made on Monday in Prague by the Security Information Service (BIS), the primary domestic national intelligence agency of the Czech Republic. Details of the alleged cyberespionage plot are included in the BIS’ annual report, a declassified version of which was released this week.

According to the document, the cyberespionage attacks were carried out by a hacker group known as APT28 or Fancy Bear, which is believed to operate under the command of Russian intelligence. The hacker group allegedly targeted the Czech Ministry of Defense, the Ministry of Foreign Affairs and the headquarters of the country’s Armed Forces. As a result, the electronic communication system of the Ministry of Foreign Affairs was compromised “at least since early 2016”, said the report (.pdf). More than 150 electronic mailboxes of ministry employees —including diplomats— were accessed, and a significant number of emails and attachments were copied by the hackers. The compromise was terminated a year later, when BIS security personnel detected the penetration. The BIS report goes on to say that a separate cyberespionage attack was carried out by a Russian-sponsored hacker group in December of 2016. An investigation into the attacks concluded that the hackers were not able to steal classified information, says the report. It adds, however, that they were able to access personal information about Czech government employees, which “may be used to launch subsequent attacks [or to] facilitate further illegitimate activities” by the hackers.

The BIS report concludes that the hacker campaign was part of “the most serious wave of cyberespionage” to target the Czech Republic in recent years. Its perpetrators appear to have targeted individuals in “virtually all the important institutions of the state” and will probably continue to do so in future attacks, it says. Moreover, other European countries probably faced similar cyberespionage breaches during the same period, though some of them may not be aware of it, according to the BIS. Czech Prime Minister Andrej Babis told parliament on Tuesday that his cabinet will discuss the BIS report findings and recommendations early in the new year.