KillNet, a pro-Russian hacker group, has claimed responsibility for a series of distributed denial of service (DDoS) attacks on NATO's cyber infrastructure and a data breach. The group declared, via Telegram, that 40% of NATO's electronic infrastructure was disabled for a period of time, listed its targets and leaked the stolen data. It also compromised 'NATO School' to obtain sensitive information, including email addresses and plaintext passwords and used the stolen credentials to register with a gay dating portal in Kyiv and Moldova.

NATO infrastructure has been targeted by KillNet before. In February, the hackers claimed responsibility for DDoS attacks that brought down the website of NATO's Special Operations Headquarters and the Strategic Airlift Capability (SAC), among others.