Tallinn - For a top-secret military base, Estonia's centre for cyber-defence looks remarkably like a genteel university. Chairs stand in neat rows in the classrooms, facing blackboards covered in arcane symbols. Vast orange armchairs ring the common room, and in one corner a coffee machine splutters belligerently.
The scene is as far from any fictional secret bunker as could be imagined, but it is a battlefield nonetheless - and one where Estonia (population 1.34 million) punches well above its weight.
"In the old days, firepower was the key to winning battles. Now it's firewalls - firewalls and cooperation," Mihkel Tammet, the jovial, bearded head of communications and IT at the Estonian Ministry of Defence, told Deutsche Presse-Agentur dpa.
Tammet should know. At the end of April, during a bitter row with Russia over the relocation of a Red Army memorial, Estonia was hit by a massive series of cyber attacks directed at government servers and banks - attacks the media called the world's first cyber-war.
"We are the first country ever to have experienced such a politically-sponsored attack on critical information infrastructure. No other countries have experienced this," Tammet said.
In a country where government meetings routinely use web-based documents, and a reported 97 per cent of banking transactions are carried out online, the effects could have been catastrophic.
"It is clear that without having applied timely and imminent countermeasures, the situation could have ... posed a significant risk to our national security," Defence Minister Jaak Aaviksoo told a conference on international security in Paris on Saturday.
Between April 27 and May 10, Estonia's cyber defenders were on high alert as the attacks threatened to break down the country's virtual walls. Estonian officials have said that some of the attacks were launched from Russian government servers.
"A small percentage of the attacks came from individuals, victims of Russian propaganda who thought they were doing the right thing in attacking us, but the majority came from robot networks which were intentionally set up by experts," Tammet said.
"It's hard to identify the people behind these "botnet" attacks, but the virtual nets have human networks behind them. Identifying those people is a job for the intelligence services," he added.
And having weathered the storm, Estonia, which only joined NATO in 2004 and whose total professional defence establishment runs to 2,300 people, has found itself lecturing NATO's biggest players on the harsh realities of the cyber age.
In the aftermath of the "cyber-war," NATO leaders gave a new priority to discussing issues of cyber defence, and the need for a solid legal framework in which to address it - debates in which Estonia's experience was of critical importance.
"Today, Estonia is an opinion leader. People are looking for answers to cyber threats, and they have started to ask for our advice; we now have to do a lot of work to move from being an opinion leader to being a leader in the field," Tammet said.
That goal may not be as distant as it sounds. Estonia has already scored a string of IT world firsts, being a leading pioneer in the worlds of online telephony and e-voting.
Its cyber-defence centre is also gaining fame, with accreditation as a NATO centre of excellence hoped for by the end of the year.
On a battlefield in which a handful of men in armchairs can play as great a role as a tank brigade, NATO's third-smallest member could yet end up as one of its biggest players in the virtual arena.
"In the cyber world, size doesn't matter," Tammet said simply.
In the eternal conflict of man against mouse, it is no longer the men who look like the winners.