A threat hunting investigation identified suspicious PowerShell content served from an IP address (203.188.171.166) and domain (dorenzaa.com), both retrieving ZIP archives from Vercel-hosted infrastructure. The PowerShell loaders extract and execute payloads locally, including Grape.exe, UltraToolliteSetup.exe, and draw.io.exe. Analysis revealed heavily obfuscated PowerShell stages utilizing Base64 encoding, XOR-based obfuscation with the key 'Write', dynamically constructed IEX commands, and hidden PowerShell execution. A decoy 'Verification complete!' message disguised as Google.com was presented to victims during execution. Multiple Vercel instances hosted additional artifacts including loader scripts and executables. The initial infection vector remains unidentified, suggesting these PowerShell-hosting URLs represent second-stage delivery points in a multi-stage attack chain.
CastleLoader, a versatile malware loader, has infected 469 devices since May 2025 using Cloudflare-themed ClickFix phishing and fake GitHub repositories. It delivers information stealers and RATs, with a 28.7% infection rate. The malware employs sophisticated techniques, including PowerShell and AutoIT scripts, to load shellcode into memory and connect to C2 servers. CastleLoader's modular design allows deployment of multiple payloads, including StealC, RedLine, NetSupport RAT, DeerStealer, HijackLoader, and SectopRAT. Its campaigns target U.S.government entities and use legitimate file-sharing services and compromised websites for payload retrieval, enhancing resilience against takedowns.
