The Trustwave SpiderLabs Threat Intelligence team's ongoing study into how threat actors use Facebook for malicious activity has uncovered a new version of the SYS01 stealer. This stealer is designed to take over Facebook accounts, steal credential information from affected users' browsers, and then leverage legitimate accounts to further the spread of the malware.
Trustwave SpiderLabs' new report, Facebook Malvertising Epidemic – Unraveling a Persistent Threat: SYS01 – Part 1, follows up on the team's February 2024 study of Ov3r_Stealer, an infostealer distributed using Facebook advertising and phishing emails that stole credentials and crypto wallets. The new report offers a granular look at SYS01, which has been operating since about September 2023, and details how the attacker conducts reconnaissance, initial access, execution, defense evasion, and mitigations and recommendations.
SYS01 is an infostealer malware, and its name was introduced by Morphisec in March 2023. Being an infostealer, SYS01 focuses on exfiltrating browser data such as credentials, history, and cookies. A big chunk of its payload is focused on obtaining access tokens for Facebook accounts, specifically those with Facebook business accounts, which can aid the threat actors in spreading the malware.
The danger SYS01 and Ov3rStealer pose is massive and obvious. Facebook has about 2.9 billion monthly active users and 200 million business accounts. With the crossover between personal and business devices, any credentials stolen through Facebook could then be used to gain initial access and establish a foothold for additional attacks against a victim's network and endpoints. From there, the floodgates could be opened to a ransomware operation, or nation-state threat actors may attempt to cause disruption, harm, or exfiltrate sensitive data.
The approach SYS01's operators use highlights how hijacking Facebook business accounts is a robust strategy that can maximize its reach and impact. Its ability to hijack Facebook business accounts, especially those with significant reach, introduces another level of approach in terms of finding ways to amplify its reach but also damages the integrity of affected businesses, which could result in tarnished reputations and financial damage.
However, these details are just a taste of the team's analysis. Please follow this link to learn the technical elements behind the malware and insights into the threat actors, communication channels, and repositories.