'Technology a blessing and curse,' says former MI5 boss

Dame Stella Rimington, the former director general of MI5, has said her job would have been much harder without technology - even if it also raised the bar in terms of the challenges she faced.

Speaking at the RSA Conference Europe in Vienna today, Rimington said technologies such as advanced encryption make intelligence gathering far more difficult but she added the pros far outweigh the cons where technology is concerned.

"Every development made in protecting information makes it more difficult for the intelligence service to access that information," she said but added that agencies must work with vendors to understand encryption and ensure nobody's technology is unwittingly protecting the terrorists.

"For every type of encryption there is a key," said Rimington. "There have been cases where encryption has been a problem momentarily but we have always overcome it."

Among the developments in the tech world which have had the greatest impact on the intelligence service, Rimington singled out battery life and size.

"The size of battery needed to power a remote microphone used to make it very difficult to conceal. It's now become a great deal easier to conceal such things," she said.

"However skilled the intelligence service is their success is going to increasingly rely upon the quality and the security of the technology they use. Although human resources are vital they must be supported and supplemented by technology."

On the controversial proposals to keep suspects in custody without trial, Rimington said this is also an issue where technology is a key consideration.

"Keeping suspects for three months without charge is outrageous to some people, quite rightly, but it may also be essential. The complexity of the data which needs to be sorted - much of which is encrypted - may mean that needs to be the case," said Rimington.

Other technologies which transformed her department during her tenure included mobile phones and the tracking on locating of calls.

Of terrorists she said: "These people do have to talk to each other and they have to communicate and that makes them vulnerable."

The ability to share information securely across multiple regions in real time also proved a major bonus to MI5, said Rimington.

"When I started, all information was put down on paper and filed. Sharing that information literally meant putting boxes of files in a van and driving them across London," said the former MI5 chief.

Rimington also spoke candidly about the intelligence service's decision to start recruiting online. She said it's a far cry from how she was recruited, which involved a secretive approach from a stranger in New Delhi.

"The days of getting the 'tap on the shoulder' are over," she said.