Dmitri Galushkevich was fined 17,500 Kroons (about $1,635) for a Denial of Service, or DoS, attack on the Web site of Estonia's governing Reform Party, led by Prime Minister Andrus Ansip.
The attack, which took the site offline for 10 days at the end of April, was part of what some analysts called the world's first act of cyberwar -- a huge wave of DoS attacks against Estonia's commercial and government Internet infrastructure, allegedly orchestrated by the Kremlin.
But 20-year-old Galushkevich admitted initiating the attack from his personal computer as an act of protest against the removal of a WWII-era war memorial to fallen Russian soldiers, Gerrit Maesalu, spokesman for the regional prosecutor's office in northeast Estonia, told reporters last week after the conviction.
Twenty-five percent of the Estonian population is ethnically Russian, and many took part in violent street protests in Tallinn as the memorial was being moved.
Analysts at the time told United Press International the Internet attacks were more like a cyber-riot -- a loosely organized outpouring of anger from Russian nationalists inside and outside the country -- than a real act of cyber-warfare.
Later last year Estonia's defense minister told a Washington audience that at least some of the attacks were carried out using a network of computers infected with special hacker software that had been rented from a criminal syndicate.
But Estonian investigators have so far charged only Galushkevich in connection with the cyber-attacks, although four ethnic Russian activists are being tried for organizing the street protests, and the alleged leader of a pro-Kremlin hacker gang Konstantin Goloskokov has been slapped with an entry ban that prevents him from getting into the European Union.
The Kremlin denied allegations last year they were involved in the attacks, but Estonian investigators have said the Russians are not co-operating with their probe.
Shaun Waterman, UPI Homeland and National Security Editor