Adrozek malware silently inject ads into search results in multiple browsers

Pierluigi Paganini December 11, 2020

Microsoft warns of a new malware named Adrozek that infects devices and hijacks Chrome, Edge, and Firefox browsers by changing their settings.

Microsoft warned of a new malware named Adrozek that infects devices and hijacks Chrome, Edge, and Firefox browsers by changing their settings and inject ads into search results pages. Users are redirected to fraudulent domains where they are tricked into installing tainted software.

Adrozek has been active since at least May 2020 and in August experts observed more than 30,000 browsers each day.

“If not detected and blocked, Adrozek adds browser extensions, modifies a specific DLL per target browser, and changes browser settings to insert additional, unauthorized ads into web pages, often on top of legitimate ads from search engines. The intended effect is for users, searching for certain keywords, to inadvertently click on these malware-inserted ads, which lead to affiliated pages.” reads the report published by Microsoft. “The attackers earn through affiliate advertising programs, which pay by amount of traffic referred to sponsored affiliated pages.”

This campaign outstands for the use of multi-browser malware that demonstrates that threat actors continue to improve their malicious code. Microsoft 365 Defender Research Team noticed that the malware is also able to achieve persistence and exfiltrates website credentials.

Microsoft experts highlighted the efforts spent by the operators to conducts the operations, they tracked 159 unique domains, each hosting an average of 17,300 unique URLs, which in turn host more than 15,300 unique, polymorphic malware samples on average.

The campaign is still active and the above infrastructure continues to expand.

“In total, from May to September 2020, we recorded hundreds of thousands of encounters of the Adrozek malware across the globe, with heavy concentration in Europe and in South Asia and Southeast Asia.” continues the report.

adrozek malware

The Adrozek malware is distributed through drive-by download, experts saw 159 unique domains used to distribute hundreds of thousands of unique malware between May and September 2020. Attackers relied heavily on polymorphism to evade detection.

Once installed, Adrozek makes multiple changes to the browser settings, it also makes changes to certain browser extensions, such as Chrome Media Router for Google Chrome.

Adrozek also modifies some of browsers’ DLL files to change browser settings and disable security features.

“Adrozek shows that even threats that are not thought of as urgent or critical are increasingly becoming more complex. And while the malware’s main goal is to inject ads and refer traffic to certain websites, the attack chain involves sophisticated behavior that allow attackers to gain a strong foothold on a device. The addition of credential theft behavior shows that attackers can expand their objectives to take advantage of the access they’re able to gain.” concludes the report.

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Pierluigi Paganini

(SecurityAffairs – hacking, Adrozek)

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