BRUSSELS - NATO defense ministers convened on Tuesday to examine cyber security as a collective defense issue amid mounting concerns over the threat posed by cyber attacks.

"We will have our first ministerial discussion dedicated to cyber defense...I believe we can do more to assist individual allies if they come under attack. That would show NATO solidarity," NATO Secretary General Ander Fogh Rasmussen said at his arrival of the two-day meeting.

In 2007, NATO member Estonia's Internet network came under massive attacks, which prompted the alliance to set up a cyber defense centre one year later in Tallin, the small Baltic country's capital. In 2011, the alliance approved a revised cyber defense policy and an action plan to strengthen cyber defense.

However, according to Rasmussen's article that was published by The Wall Street Journal on Sunday, cyber defense is still primarily a job for individual nations and governments while NATO's role is largely limited to protect its internal networks.

"But as the threats continue to evolve, NATO should be prepared to consider an enhanced role...NATO protected its members during the age of the Berlin Wall. We must be prepared to protect them during the age of the firewall," it said.

The NATO defense minister are also expected to endorse the concept for NATO's new mission in Afghanistan after 2014, when all NATO combat troops are scheduled to leave the Central Asia country.

"We will adopt what we call a concept of operations and a concept means broad guidelines for how we will shape the future Resolute Support mission from 2015," Rasmussen told reporters.

"It will be very different mission; it will be a non-combat mission. The number of troops and trainers will be significantly lower than in the current ISAF mission and it's also our intention to ensure a regional foot-print, that is a number of regional training centers," he said.

Syria is not an official agenda item, but NATO officials said the issue could be discussed on the margins of the meeting.

Rasmussen said earlier this year that the alliance's computer systems are under "regular" attacks, but "so far we have successfully protected our systems."

"We have to take it seriously and consider how we can strengthen our cyber defense...We need the political push," he said.