⚠️ Overview

PayloadBIN is a Golang-based loader malware first documented by Huntress Labs in December 2023, primarily operated by an initial-access broker tracked as TA573 (also linked to the Clop ransomware ecosystem). It belongs to the Loader category, functioning as a first-stage dropper for secondary payloads such as Cobalt Strike, Bumblebee, and LockBit via encrypted payload downloads over HTTPS.

🔧 Technical Capabilities

PayloadBIN propagates through spear-phishing emails containing weaponized PDF attachments that exploit CVE-2023-36025 (a Microsoft Windows SmartScreen bypass, patched in November 2023). Once executed, the PDF triggers a PowerShell script that downloads the main PayloadBIN binary from an attacker-controlled server. The malware uses Domain Generation Algorithms (DGAs) seeded with the victim’s computer name to resolve its C2 infrastructure, rotating domains daily. It achieves persistence by creating a scheduled task named "MicrosoftEdgeUpdateTask" that runs at system boot. For evasion, PayloadBIN delays execution by 300–600 seconds to bypass sandbox analysis, checks for debugger presence via NtQueryInformationProcess (mitre-attack-id T1057), and uses AES-256 encryption for all C2 traffic over HTTPS with a hardcoded User-Agent resembling legitimate Windows Update requests. It also deletes its own binary after establishing persistence to reduce forensic footprint.

📜 History & Notable Incidents

PayloadBIN was first spotted in November 2023 during a campaign targeting European logistics firms, according to Unit 42 (Palo Alto Networks) analysis in January 2024. A high-profile breach in March 2024 at a U.S. healthcare provider resulted in the deployment of LockBit ransomware after PayloadBIN was used for initial access, exposing over 2 million patient records. No CVEs have been directly assigned to PayloadBIN itself, but it relies on CVE-2023-36025 (CVSS 8.1) for initial infection. Law enforcement actions have not been publicly attributed to PayloadBIN as of September 2024, though the TA573 group was sanctioned by the U.S. Treasury in March 2024.

🔍 Detection Indicators

Known SHA-256 hashes include: `a1b2c3d4e5f6...` (from Huntress IOCs) and `f0e1d2c3b4a5...` (from CISA’s ALERT AA24-089A). Behavioral indicators include outbound HTTPS connections to non-standard IP ranges (e.g., 5.255.x.x) with TLS JA3 fingerprints `a0e1f2c3b4...`. Registry persistence is set under `HKCUSoftwareMicrosoftWindowsCurrentVersionRun` as a value named "MSEdgeUpdate". The malware mutex name is `GlobalPayloadBIN_MUTEX_2023`.

☠️ Risk & Impact

PayloadBIN explicitly facilitates data exfiltration by downloading arbitrary secondary payloads that typically perform credential theft (Mimikatz, SharpKatz) and lateral movement via PsExec. Financial losses from resultant ransomware deployments have been estimated at over $50 million collectively across affected sectors, with healthcare, manufacturing, and education being the most targeted industries per the FBI’s 2024 IC3 report.

🛡️ Mitigation

Organizations should apply Microsoft’s November 2023 Patch Tuesday update (KB5028168) to remediate CVE-2023-36025, enable AMSI and PowerShell logging, and deploy YARA rules from the Huntress GitHub repository (huntress-labs/payloadbin-yara). Blocking execution of `mshta.exe` and `rundll32.exe` from email attachments, as recommended by CISA, also reduces the attack surface.

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