Cybersecurity researchers have uncovered a never-before-seen dropper that serves as a conduit to launch next-stage malware with the last word purpose of infecting Home windows techniques with info stealers and loaders.
“This memory-only dropper decrypts and executes a PowerShell-based downloader,” Google-owned Mandiant mentioned. “This PowerShell-based downloader is being tracked as PEAKLIGHT.”
A number of the malware strains distributed utilizing this method are Lumma Stealer, Hijack Loader (aka DOILoader, IDAT Loader, or SHADOWLADDER), and CryptBot, all of that are marketed beneath the malware-as-a-service (SaaS) mannequin.
The start line of the assault chain is a Home windows shortcut (LNK) file that is downloaded through drive-by obtain strategies — e.g., when customers lookup a film on search engines like google and yahoo. It is value stating that the LNK information are distributed inside ZIP archives which might be disguised as pirated films.
The LNK file connects to a content material supply community (CDN) internet hosting an obfuscated memory-only JavaScript dropper. The dropper subsequently executes the PEAKLIGHT PowerShell downloader script on the host, which then reaches out to a command-and-control (C2) server to fetch extra payloads.
Mandiant mentioned it recognized completely different variations of the LNK information, a few of which leverage asterisks (*) as wildcards to launch the professional mshta.exe binary to discreetly run malicious code (i.e., the dropper) retrieved from a distant server.
In the same vein, the droppers have been discovered to embed each hex-encoded and Base64-encoded PowerShell payloads which might be ultimately unpacked to execute PEAKLIGHT, which is designed to ship next-stage malware on a compromised system whereas concurrently downloading a professional film trailer, doubtless as a ruse.
“PEAKLIGHT is an obfuscated PowerShell-based downloader that’s a part of a multi-stage execution chain that checks for the presence of ZIP archives in hard-coded file paths,” Mandiant researchers Aaron Lee and Praveeth D’Souza mentioned.
“If the archives don’t exist, the downloader will attain out to a CDN web site and obtain the remotely hosted archive file and reserve it to disk.”
The disclosure comes as Malwarebytes detailed a malvertising marketing campaign that employs fraudulent Google Search advertisements for Slack, an enterprise communications platform, to direct customers to phony web sites internet hosting malicious installers that culminate within the deployment of a distant entry trojan named SectopRAT.