Microsoft said that major internet browsers — Chrome, Firefox, Microsoft Edge, Yandex – were hit by a massive malware called Adrozek, designed to inject ads into search engine results pages. The campaign has been active since at least May 2020 and reached August. The threat was observed on over 30,000 devices every day. Adrozek adds browser extensions, modifies a specific DLL, and changes browser settings. Mozilla Firefox was the worst affected.