Estonia has signed an agreement with NATO (which Estonia is a member of) to facilitate cooperation between NATO and Estonia if Estonia is hit by another Internet based attack. Two years ago, NATO established a Cyber Defense Center in Estonia. This, and the recent agreement, is a result of being called on by Estonia, three years ago, to declare Cyber War on Russia. That was because Russia was accused of causing great financial harm to Estonia via Cyber War attacks, and Estonia wanted this sort of thing declared terrorism, and dealt with. NATO agreed to discuss the issue, but never took any action against Russia. The new agreement creates a legal framework for striking back, or at least to defend Estonia more vigorously if there is another attack.
The Cyber Defense Center was established to study Cyber War techniques and incidents, and attempt to coordinate efforts with other NATO members to create Cyber War defenses, as well as offensive weapons. The recent agreement is one product of that research. Another is greater awareness among NATO nations of what the threat is, and how serious it is. Similar agreements have already been signed with Slovakia, Turkey, Britain and the United States.
Cyber Wars have been going on for over a decade now, and they are getting worse. It started in the 1990s, as individuals attacked the web sites in other nations because of diplomatic disputes. This was usually stirred up by some international incident. India and Pakistan went at it several times, and Arabs and Israelis have been trashing each other's web sites for years. The Arabs have backed off somewhat, mainly because the Israeli hackers are much more effective. Chinese and Taiwanese hackers go at each other periodically, and in 2001, Chinese and American hackers clashed because of a collision off the Chinese coast between an American reconnaissance aircraft and a Chinese fighter.
In the last five years, these Cyber Wars have escalated from web site defacing and shutting down sites with massive amounts of junk traffic (DDOS attacks), to elaborate espionage efforts against American military networks. The attackers are believed to be Chinese, and some American military commanders are calling for a more active defense (namely, a counterattack) to deal with the matter.
The Russian attacks against Estonia were the result of Estonia moving a statue, honoring Russian World War II soldiers, from the center of the capital, to a military cemetery. The Estonians always saw the statue as a reminder of half a century of Russian occupation and oppression. Russia saw the statue move as an insult to the efforts of Russian soldiers to liberate Estonia, and enable the Russians to occupy the place for half a century. The basic problem here is that most Russians don't see their Soviet era ancestors as evil people, despite the millions of Russians and non-Russians killed by the Soviet secret police. The Russians are very proud of their defeat of Nazi Germany in World War II, ignoring the fact that, back then, the Soviet government was just biding its time before it launched its own invasion of Germany and Europe in general.
While many Russians would have backed a military attack on Estonia, to retaliate for the insult by an ungrateful neighbor, this approach was seen as imprudent. Estonia, as a NATO member, is protected because an attack on one NATO member is considered an attack on all. It's because of this Russian threat that Estonia was so eager to get into NATO. The Russians, however, believe that massive Cyber War attacks will not trigger a NATO response. They were so sure of this, that some of the early DDOS attacks were easily traced back to computers owned by the Russian government. When that got out, the attacks stopped for a few days, and then resumed from what appear to be illegal botnets. Maybe some legal botnets as well. Russian language message boards were full of useful information on how to join the holy war against evil Estonia. There's no indication that any Russians are afraid of a visit from the Russian cyber-police for any damage they might do to Estonia. And the damage has been significant, amounting to millions of dollars so far. While no one has been injured, Estonia is insisting that this attack, by Russia, should trigger the mutual defense provisions of the NATO treaty. It didn't, but it was a reminder to all that Cyber War is very real.