Cybersecurity researchers have recently uncovered a significant malvertising campaign that exploits Meta’s advertising platform and hijacks Facebook accounts to distribute the SYS01stealer malware. Bitdefender Labs reported that the attackers behind this campaign leverage trusted brands to expand their reach, utilizing nearly one hundred malicious domains not only for distributing the malware but also for conducting live command and control operations.
This strategy allows the threat actors to manage their attacks in real-time, increasing the effectiveness and reach of the malware. The SYS01stealer malware was initially documented by Morphisec in early 2023, highlighting its use in campaigns targeting Facebook business accounts through Google ads and fake Facebook profiles.
These profiles often promote games, adult content, and cracked software. The malware’s primary goal is to steal sensitive information such as login credentials, browsing history, and cookies, with a particular focus on acquiring Facebook ad and business account data. This stolen data is then utilized to propagate the malware further by creating and distributing phony ads. The malvertising campaign primarily targets users through platforms like Facebook, YouTube, and LinkedIn, with ads promoting various products, including Windows themes, games, AI software, photo editors, VPNs, and movie streaming services. Most of these Facebook ads are specifically engineered to attract men aged 45 and older.
The ads entice victims into clicking, leading to the theft of their browser data. If Facebook-related information is included in the stolen data, there’s a risk of further compromise, as the threat actors can take control of the victims’ Facebook accounts to spread more malvertisements and continue the cycle of infection. In the latest attack chains, the first-stage payload is delivered as a ZIP archive containing a benign executable, which sideloads a malicious DLL responsible for launching a multi-stage infection process.
This includes running PowerShell commands to evade detection, modifying Microsoft Defender Antivirus settings, and establishing an environment to operate the PHP-based stealer. Bitdefender noted the adaptability of the cybercriminals involved, as they swiftly update their code in response to security measures implemented by cybersecurity firms. This constant evolution makes the SYS01stealer campaign particularly dangerous, as the malware employs techniques to detect sandbox environments used by analysts, allowing it to evade detection and continue its malicious activities.
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