Unknown hackers breached the UK railway network four times in the last twelve months, according to Darktrace, a British cyber-security firm, quoted by The Telegraph and Sky News.

According to Darktrace, the attacks were only basic reconnaissance operations, intrusions to detect a network's internal structure and to gather information for future attacks. The company also doesn't exclude that these intrusions were only accidental.

Previous to the UK, attacks on a country's railway network were detected in Ukraine this past winter, as part of the infamous BlacEnergy attacks that also targeted the country's energy grid and airports.

Railway networks are part of a country's transportation system and are considered "critical infrastructure."

In the case of a real cyber-war, railway networks, along with smart roads and airports, are most certainly going to face cyber-attacks, along with the other critical infrastructure sectors such as energy, water supply, oil & gas, communications, the chemical sector, food & agriculture, healthcare, and emergency services.

Attacks on a railway network's infrastructure are technically possible

This past December, at the 32nd Chaos Communication Congress (32C3) in Germany, Russian security researchers from SCADA StrangeLove presented a series of attacks that could cripple a railway network.

These attacks rely on targeting a network's rail automation and route planning components situated on the network itself, but also train control components and tracking systems installed on the train carts and locomotives.

A successful attack on the first would allow an intruder to successfully alter a railway network's routes and train track switches.

An attack on the second would allow the intruder to feed trains bad location data, or disrupt communications with the central railway command center.

Based on the attack type an intruder wants to execute and their knowledge of a network's internal components, successful attacks can vary from simple delays to train crashes that can lead to loss of human life.