Hackers hit three Greek banks with ransom demands

Hackers have staged cyber-attacks on three Greek banks and demanded a ransom in bitcoins, a virtual monetary unit, to stop their disruption, banking sources said on Monday.

The sources said the hackers managed to block the Internet banking activity of three Greek lenders for a few hours last Thursday but did not penetrate the banks' security or obtain confidential client data or access to accounts.

"All they achieved was to block the web banking for a few hours. Nothing else," one banker told Reuters, speaking on condition of anonymity. The sources said the hackers had given the name of their group as Armada Collective.