SystemBC (Coroxy / DroxiDat) Malware: Multi-Purpose SOCKS5/Tor Proxy Backdoor Enabling Ransomware Operations — Threadlinqs Intelligence
As of 2026-07-11, SystemBC (Coroxy / DroxiDat) Malware: Multi-Purpose SOCKS5/Tor Proxy Backdoor Enabling Ransomware Operations is a high-severity malware threat attributed to Periwinkle Tempest (RU), tracked by Threadlinqs Intelligence with 9 detection rules (Splunk SPL, Microsoft KQL, Sigma) and 36 indicators of compromise.
Threat ID: TL-2026-1227 · Severity: HIGH · Status: ACTIVE · Category: MALWARE
Attribution: Periwinkle Tempest · RU · FINANCIAL
SystemBC (aka Coroxy, DroxiDat) is a Windows-only backdoor/RAT sold as malware-as-a-service that converts infected hosts into SOCKS5 (and, in newer variants, Tor) proxies to tunnel other malware's C2
SystemBC is a commodity Windows backdoor first documented in 2018 that has evolved into a persistent "Swiss-army-knife" tool in the ransomware ecosystem. It is typically delivered via exploit kits (historically RIG, Fallout) or dropped by loader malware (Emotet, QBot/Qakbot, Buer Loader) after initial compromise, and by threat actors such as Wizard Spider (since 2020) and FIN7 (since 2022), as well as financially motivated intrusion sets tracked as Pistachio Tempest/FIN12.
Once deployed, SystemBC establishes persistence via a Registry Run key (commonly under `HKCU\Software\Microsoft\Windows\CurrentVersion\Run`, value name "socks5") and/or a scheduled task with a randomly named `.job` file under `C:\Windows\Tasks\`. The malware copies itself into a randomly named subdirectory of `%ProgramData%` and re-registers the copy as a scheduled task invoked with a "start" argument. It performs anti-analysis checks, including skipping persistence installation when Emsisoft's `a2guard.exe` process is detected.
C2 communication begins with a 100-byte beacon: a 50-byte plaintext RC4 key followed by 50 bytes of RC4-encrypted host/user reconnaissance data (machine name, username, IP address, volume serial number). Configuration data is stored/obfuscated in memory using a 40-byte XOR key. The malware supports resolution of `.bit` pseudo-domains via alternate/custom DNS infrastructure (observed using OpenNIC resolvers such as ns1.vic.au.dns.opennic.glue and ns2.vic.au.dns.opennic.glue), and newer variants embed a mini-tor-based Tor client (using Windows BCrypt/CNG cryptographic APIs) to route C2 over the Tor network, hardcoding Tor directory authority IPs (193.23.244.244, 86.59.21.38, 199.58.81.140, 204.13.164.118) to bootstrap circuits without relying on the public Tor consensus fetch. The default C2 listener port is TCP/4001; the SOCKS5 proxy component is advertised on underground forums as supporting configurable ports and up to 40,000 concurrent proxied connections.
SystemBC operates as both a RAT and a loader: it can execute arbitrary EXE, DLL, shellcode, VBS, BAT, CMD, and PowerShell payloads pushed from its operator, including in-memory (reflective) execution to minimize disk artifacts. This lets ransomware affiliates use a single implant for discovery, credential/lateral-movement tooling delivery, and traffic tunneling that evades network-based detection (since ransomware C2/exfil traffic egresses through the compromised host's SOCKS5/Tor tunnel rather than a directly attributable ransomware C2 address).
A closely related lightweight variant tracked as DroxiDat (~8KB) was observed in March 2023 in an intrusion against a healthcare-sector target in southern Africa, functioning purely as a system profiler/lightweight SystemBC client that collected host information and staged a Cobalt Strike beacon from the same infrastructure cluster before the intrusion proceeded toward Nokoyawa ransomware deployment. That incident used a `C:\perflogs\` staging directory and C2 domains with power/energy-industry-themed naming (`powersupportplan[.]com`, `epowersoftware[.]com`), suggesting deliberate blending into critical-infrastructure/utility-sector network traffic; Kaspersky attributed the cluster to Pistachio Tempest/FIN12 with low confidence based on staging-directory reuse and shared Cobalt Strike license IDs across incidents.
SystemBC's persistent value to ransomware affiliates comes from decoupling proxy/tunneling infrastructure from the ransomware payload itself: defenders who block or attribute ransomware C2 domains do not automatically disrupt the SystemBC tunnel, and the SOCKS5/Tor layer can be reused across multiple ransomware deployments and affiliates purchasing the same malware-as-a-service kit.
Target sectors: critical infrastructure, energy, health, government administration, finance, manufacturing, retail, education
Target regions: North America, Europe, Africa, Global
Detections & IOCs
As of 2026-07-28, this threat has 9 detection rule(s) across Splunk SPL, Microsoft KQL and Sigma, and 36 indicator(s) of compromise. Detection query text and full IOC values are available to authenticated users and programmatically via the Threadlinqs MCP server (Purple tier). View plans.
MALWARE, HIGH, threat intelligence, cybersecurity, T1189, T1059, T1059.001, T1059.003, T1059.005, T1106, T1547.001, T1053, T1053.005, T1001