Fitness app accidentally reveals secrets of French nuclear submarine

France currently operates four nuclear ballistic missile submarines, with one always at sea to ensure a counterattack in the event of a surprise attack.

The ships were deployed from the Ile Longue base near the port of Brest, which is heavily guarded by a variety of security measures, including security scans, facial recognition and sniffer dogs.

However, Le Monde said some staff at the base used the Strava app to record their workout data, inadvertently revealing important information about submarine patrol schedules.

By tracking exercise activities, such as running or cycling, adversaries could deduce periods of time when sailors disappeared from the app, which could be correlated with the submarine's patrol schedule.

One notable example is a sailor who posted a workout on Strava, lamenting, “It’s hard to get back to training after being in a little box for over two and a half months,” along with a mask and bubble emoji. According to Strava data, the sailor ran a 45-minute 10K run before going 50 days without any activity.

On the same day, two other sailors were also seen jogging around the dock area where the submarines were docked, before “disappearing” around the same time. Although the submarines’ patrol schedules are classified, details from the app revealed the deployment times.

According to Le Monde, the newspaper calculated the departure dates and patrol times of four recent missions. Knowing the departure dates could allow an adversary to place sensors at the base exit to track the submarine as it heads out to sea, thereby undermining the effectiveness of the strategic deterrence mission.

The French Navy has acknowledged the negligence of some individuals, but stressed that this did not necessarily affect the operations of the base. However, the incident raises concerns about the level of security in the use of smart devices at important military facilities.

While all electronic devices, including cell phones, must be kept in lockers at checkpoints, smartwatches appear to be an exception. These devices allow sailors to record training data and GPS locations while on base, then upload them to an app when they return to shore.

According to Le Monde, more than 450 employees at the Ile Longue base have used the Strava app over the past decade. Data from the app could allow adversaries to track the activities of the base and submarines, threatening the core mission of nuclear submarines, which is to ensure strategic deterrence.

France’s Triomphant-class nuclear submarines are considered a key element of the country’s nuclear deterrent strategy. Each carries 16 ballistic missiles, each equipped with multiple thermonuclear warheads. Since 1972, France has maintained at least one nuclear submarine at sea.