Europol police chief Rob Wainwright has warns sophisticated online communications are the biggest problem for security agencies tackling terrorism.Encryption is one of the most basic technique used by tech companies to protect their users' communications. It involves encoding messages that people send, allowing only people or devices that have a key can unlock them.
The "hidden internet" is a layer of database and websites that aren't indexed by regular search engines like Google. This so-called "deep web" lies beneath the "surface web" which is what individuals typically use everyday.
Accirding to BBC, Mr Wainwright was talking to 5 Live Investigates.A spokesman for TechUK, the UK's technology trade association, said: "With the right resources and cooperation between the security agencies and technology companies, alongside a clear legal framework for that cooperation, we can ensure both national security and economic security are upheld."
Mr Wainwright said that in most current investigations the use of encrypted communications was found to be central to the way terrorists operated.
"It's become perhaps the biggest problem for the police and the security service authorities in dealing with the threats from terrorism," he explained.
"It's changed the very nature of counter-terrorist work from one that has been traditionally reliant on having good monitoring capability of communications to one that essentially doesn't provide that anymore."
Mr Wainwright, whose organisation supports police forces in Europe, said terrorists were exploiting the "dark net", where users can go online anonymously, away from the gaze of police and security services.
Mr Wainwright acknowledged this was a result of the revelations by former National Security Agency contractor Edward Snowden, who exposed how security services were conducting widespread surveillance of emails and messages.
Europol is now setting up a European Internet Referral Unit to identify and remove sites being used by terrorist organisations.
Mr Wainwright also says current laws are "deficient" and should be reviewed to ensure security agencies are able to monitor all areas of the online world.
He said security agencies now had to work to rebuild trust between technology firms and the authorities
