"This is the first time banks and internet companies have been part of an EU-wide cyber-attack exercise," said European Commission Vice-President Neelie Kroes, in charge of the Digital Agenda.
The exercise, named Cyber Europe 2012, simulates a sustained attack against the public websites and computer systems of major European banks. It started this morning at around 09:00 am Brussels time and will continue throughout the day, a Commission spokesperson told EurActiv.
No real infrastructures are involved, the Commission said.
The exercise involves the simulation of more than 1,200 separate cyber incidents, including more than 30,000 emails, during a simulated distributed denial of service (DDoS) campaign, the EU executive said in a statement.
If real, such a cyberattack would cause massive disruption for millions of citizens and businesses across Europe, and millions of euros of damage to the EU economy, the EU Executive said, adding that the exercise is testing how they would respond and co-operate.
Kroes said such cooperation was "essential given the growing scale and sophistication of cyber-attacks. Working together at European level to keep the internet and other essential infrastructures running is what today's exercise is all about".
This is the second cyberattack exercise carried out under the supervision of the European Network and Information Security Agency (ENISA), based in Heraklion, Greece.
The first, conducted in 2010, tested collaboration between national public authorities in countering a simulated attempt by hackers to paralyse the internet and critical online services across Europe.
ENISA will publish initial results of the 2012 simulation in the coming days and publish a detailed report with key findings before the end of the year.
A full report on the evaluation of the 2010 exercise is available here.