Analysis: hackers eye up fibre optic data networks

Encryption firm infoGuard has warned that transmitting data over fibre optic cable, a process seen by many as hacker-proof, is not totally secure.

The prevailing wisdom, held by bodies including the European Parliament, that fibre optic cables can only be tapped at end nodes is no longer valid, according to infoGuard.

The firm asserts that there are various optical tapping methods that can be used to extract data from fibre optic networks.

As with traditional copper networks, signals travelling long distances over fibre optic cable become attenuated and pass through amplifiers which boost the signal for the next leg of its journey.

Most of these points are clearly marked for maintenance purposes and can provide an easy point of intrusion.

The risk of being detected is very slight and the tools to do it are easily available, infoGuard warned.

Optical tapping methods can be divided into three categories. The 'splice method' involves literally breaking the cable at some point and adding a splitter.

This is the oldest and most obvious method but, although easily detectable due to the break in service, the downtime is usually very short and is often put down to a minor glitch.

The 'splitter/coupler method' involves bending the cable to a certain radius, which allows a small amount of the transmitted light to escape.

Thanks to advances in optical detectors, just 0.1dB of the optical rating is required to obtain the full signal.

This method does not require the service to be interrupted, but can be detected owing to the attenuation of the signal caused by the bending of the cable.

But the latest and most insidious 'non-touching methods' involve highly sensitive photo-detectors that capture the tiny amounts of light that emerge laterally from the glass fibre owing to a phenomenon known as Rayleigh scattering.

InfoGuard warned that the only sensible course of action to guard against intrusions of this nature is to encrypt the information being transmitted prior to connecting to the public networks.

Fibre optic networks are employed by banks, financial institutions, enterprises and public authorities as a backbone, which makes it a prime target for industrial espionage.

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