The UK Ministry of Defence (MoD) is reportedly investigating claims that Russian hackers accessed and stole hundreds of sensitive files and then leaked the information on the dark web.

According to reporting, the alleged data theft involves a contractor used to maintain and support defence facilities. The files are said to include details tied to multiple RAF and Royal Navy bases, as well as the names and email addresses of MoD staff. Among the locations mentioned in the reporting is RAF Lakenheath in Suffolk, a base associated with US F-35 aircraft operations.

The MoD said it is actively investigating whether information relating to the department has been published online, adding that it would not comment on further details to protect sensitive operational information.

The contractor involved has also acknowledged a ransomware incident, saying it took steps to contain the intrusion, secure its systems, and bring in specialist forensic support to assess what happened and whether any data was accessed.

The investigation comes amid a wider context of security incidents affecting UK government-linked organisations, with authorities and cybersecurity experts warning that stolen credentials or access—whether used for direct exploitation or resale—can create significant risk to national security and public services.