CERT Orange Cyberdefense
2.9 KiB
🧵 Since March 2026, Orange Cyberdefense has been tracking a malware delivery cluster linking a fake FileZilla campaign with other software-themed lures, including LibreOffice and Google Drive Setup, as well as a ClickFix-based one. Our investigation identified overlaps across these campaigns, and related samples were later publicly identified as STX RAT.
#CTI #ThreatIntel #STXRAT
1/ Our investigation started from the publicly documented FileZilla campaign, which used a fake FileZilla website to distribute trojanized FileZilla 3.69.5 packages. The campaign used two delivery variants: a portable archive containing the legitimate FileZilla package plus a malicious version.dll a single EXE installer dropping the same DLL during installation In both cases, filezilla.exe sideloaded the DLL and triggered a staged infection chain that ultimately delivered a RAT.
2/ We identified overlaps with: a malvertising chain using VBS lures impersonating Google Drive or LibreOffice a ClickFix lure reported by a private source These branches were supported by shared infrastructure and staging patterns.
3/ Key overlap points included infrastructure involving supp0v3[.]com, cdn0v3[.]com, and 147.45.178[.]61, multiple pages[.]dev staging hosts, and similar callback / tracking logic observed across the linked chains.
4/ In the FileZilla branch, the sideloaded loader performed anti-analysis and anti-virtualization checks, resolved C2 via DNS-over-HTTPS, and used callback logic with tracking parameters. In the overlapping script-based activity we tracked, VBS / PowerShell stages and TAR-delivered components (1.bin and 2.txt) led to in-memory payload execution.
5/ Separately, eSentire later described a related script-based branch involving VBScript → JScript → TAR (1.bin + 2.txt) → PowerShell, which is consistent with the broader staging logic we observed across the cluster. At the malware level, STX RAT is a Windows RAT with infostealer and HVNC capabilities. It uses a custom multi-stage unpacking chain, communicates over a proprietary TCP-based protocol with both clearweb and Tor fallback, and exposes broad post-exploitation functionality. Notably, credential theft is only activated after successful C2 interaction.
6/ Bottom line: different lures, similar staging, same malware outcome.
7/ We published a full advisory for our customers on the infection chain, overlaps, and malware analysis. Related IoCs are also available in this public GitHub repository.
Sources:
eSentire: https://www.esentire.com/blog/stx-rat-a-new-rat-in-2026-with-infostealer-capabilities
Alyac: https://blog.alyac.co.kr/5738
Jerome Segura: https://jeromesegura.com/malvertising/2026/01/01-20-2026_LibreOffice
Other STX RAT campaigns:
CPUID: https://x.com/d0cTB/status/2042520961824559150
Kaspersky: https://securelist.com/tr/cpu-z/119365/