NSA warns of growing state-backed threats

The deputy director of the US National Security Agency (NSA), Richard Ledgett, has warned of the increasing danger of destructive cyber attacks by states.

He told the BBC: "If you are connected to the internet, you are vulnerable to determined nation-state attackers." He said nations would need to identify red lines that should not be crossed.

He also said agency targets, numbered in "the high hundreds", had discussed leaks by contractor Edward Snowden, with some changing their behaviour.

In cyberspace, Ledgett said the agency was seeing a shift to more destructive attacks - such as those that hit Sony last year or Saudi Aramco in 2012 - as well as more aggressive postures by nation states.

Meanwhile, CIA chief John Brennan said yesterday he was "outraged" that hackers broke into his personal email account, and faulted the media for its coverage of the incident.

WikiLeaks, the anti-secrecy group, began releasing documents from Brennan's private AOL account last week, days after a teenage hacker was reported to have claimed he had gained access to the account.

The documents released so far have included a contact list, policy recommendations on Afghanistan and Pakistan, and his family's addresses and phone numbers.