Nearly a million Windows computers impacted by a malvertising campaign

Microsoft Threat Intelligence reports that the campaign was launched in December 2024: unknown attackers started distributing links that loaded ads. Microsoft claims that websites hosting such ads were illegal streaming websites offering pirated videos. The company’s report mentions two streaming website domains: movies7[.]net and 0123movie[.]art.

“The streaming websites embedded malvertising redirectors within movie frames to generate pay-per-view or pay-per-click revenue from malvertising platforms,” – Microsoft.

Malicious links contained within an iframe were taking victims through a chain of redirects and a number of intermediate sites (e.g. a scam tech support site) ultimately leading to GitHub repositories containing a variety of malicious files.

Malware was deployed in several stages. At early stages, information on the user’s device was collected, presumably to configure subsequent attack stages. At later stages, malware detectors were disabled, a connection was established with control servers, and the NetSupport remote monitoring and management software was installed.

“Depending on the second-stage payload, either one or multiple executables are dropped onto the compromised device, and sometimes an accompanying encoded PowerShell script. These files initiate a chain of events that conduct command execution, payload delivery, defensive evasion, persistence, C2 communications, and data exfiltration,” – Microsoft.

In addition to GitHub, payloads were also hosted on Discord and Dropbox.

Microsoft experts believe that this campaign was opportunistic in nature (i.e. the cybercriminals attacked everyone without distinction and didn’t target specific persons, companies, or industries). As a result, devices belonging to both individuals and various organizations were impacted.

After penetrating into the victim’s system, the malware (mostly the Lumma stealer or an updated version of the Doenerium open-source info stealer) accessed browser data files to steal login cookies, passwords, histories, and other sensitive information:

• AppDataRoamingMozillaFirefoxProfiles<user profile uid>.default-releasecookies.sqlite;
• AppDataRoamingMozillaFirefoxProfiles<user profile uid>.default-releaseformhistory.sqlite;
• AppDataRoamingMozillaFirefoxProfiles<user profile uid>.default-releasekey4.db;
• AppDataRoamingMozillaFirefoxProfiles<user profile uid>.default-releaselogins.json;
• AppDataLocalGoogleChromeUser DataDefaultWeb Data;
• AppDataLocalGoogleChromeUser DataDefaultLogin Data; and 
• AppDataLocalMicrosoftEdgeUser DataDefaultLogin Data.

The attackers also attempted to access files stored on Microsoft OneDrive and scanned infected systems for cryptocurrency wallets, including Ledger Live, Trezor Suite, KeepKey, BCVault, OneKey, and BitBox.

According to Microsoft, first-stage reports were digitally signed with a newly-created certificate. In total, 12 certificates used in the malvertising campaign were identified and subsequently revoked by the company.