Microsoft has issued a warning about Adrozek, a new strain of browser modifier that, according to the company, "adds browser extensions, modifies a specific DLL per target browser, and changes browser settings to insert additional, unauthorized ads into web pages."
According to Microsoft, the malware is being distributed by large, well-funded, and organized groups. In the blog post warning about Adrozek, Microsoft researchers say that in their tracking of the Adrozek campaign from May to September, they found 159 unique domains used in attacks. While many of those domains hosted tens of thousands of URLs, they say that a few had more than 100,000 unique URLs, with one hosting almost 250,000.
They found hundreds of thousands of unique, heavily obfuscated, Adrozek installers. Once installed, the malware makes changes to several browser extensions and .DLLs. Both Firefox and Chromium-based browsers are susceptible to Adrozek. Researchers recommend a number of practices, including limiting available URLs and restricting software that can be installed, as methods that can help limit the impact of Adrozek and similar malware.
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