Starting at 22:47 Kyiv time on Nov 1 (3:47 PM ET), the official Air Alert app ("Povitriana tryvoha"), backed by Ukraine's Ministry of Digital Transformation and built with Ajax Systems, pushed false alerts: a radiation threat in Kyiv, a chemical-attack threat, a street-fighting threat, and a Russian-language message saying a nuclear alert was coming across Ukraine because an Oreshnik missile was on its way. All-clear messages followed. Officials warned the messages may carry a phishing link and told people not to click it.

The Air Force said the app had "probably been subjected to hostile interference" and that there was no radiation threat; its spokesperson Yurii Ihnat told Ukrainska Pravda that it had announced no radiation or other threats that evening. Ukraine's Center for Countering Disinformation also called the app likely compromised. The BBC reports that the radiation-hazard signal was played through loudspeaker devices in Lviv region. The State Emergency Service said the national street-siren system itself kept working normally.

The app team confirmed the hack, suspended the app, and early on Nov 2 restored push alerts and the yellow and red threat levels while keeping target display on the map turned off. It says the app stores no personal data. How the attackers got in has not been disclosed, and no group has been publicly attributed.