Tiny Estonia (population 1.3 million) has formed a Cyber War militia because Russia keeps threatening another major Cyber War offensive. Despite its small size Estonia is the most technically advanced (on a per-capita basis) nation in East Europe and was able to recruit several hundred skilled volunteers who are hard at work pooling their knowledge and skills to better handle more Cyber War aggression from Russia.
Estonia borders Russia and is a member of NATO. That last bit makes Russia reluctant to come in with tanks to take over like they did twice in the 1940s. Russia made a major effort to crush Estonia via major Internet based attacks in 2007. Estonia survived that “invasion” but admitted that this sort of Russian aggression caused great financial harm to Estonia. In the wake of these Russian Cyber War attacks Estonia demanded that the UN and NATO declare this sort of thing terrorism and dealt with accordingly. NATO tried to be helpful, but that wasn’t enough. The UN was even less helpful as the UN has a hard time getting anything done when Russia is involved because Russia is one of the handful of founding members that has a veto.
NATO did make an effort and in 2008 established a Cyber Defense Center in Estonia. This was the most tangible NATO response to Estonian calls for NATO to declare Cyber War on Russia. NATO agreed to discuss the issue but never took any action against Russia. The Cyber Defense Center was a consolation prize and studies Cyber War techniques and incidents and attempts to coordinate efforts by other NATO members to create Cyber War defenses and offensive weapons. NATO say that this appears to have deterred Russia from making another Cyber War attack. The Estonians are not so sure as Russia went ahead and invaded Georgia (a nation of four million in the Caucasus) in 2008 and Ukraine in 2014 and still makes very public threats against Estonia.
Cyber Wars have actually been going on since the late 1990s 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 backed off at first, mainly because the Israeli hackers are much more effective. But in the last few years the Arabs have acquired more skills and are back at it. 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. That was just the beginning for China, which now regularly makes major hacking attacks on the U.S. and other NATO members.
Since 2005 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 in the countryside. 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 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 is part of NATO and 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. 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 except when it comes time to fight back.