SilentSync RAT Hides in Plain Sight on PyPI

SilentSync RAT: Supply-Chain Attack via Malicious PyPI Packages

Summary

In August 2025, security researchers uncovered two malicious Python packages, sisaws and secmeasure, uploaded to PyPI as part of a global supply-chain attack. These packages secretly delivered SilentSync, a cross-platform Remote Access Trojan (RAT) targeting Windows, Linux, and macOS.

SilentSync enables attackers to gain persistence, remote control, credential theft, file exfiltration, and screenshot capture. This incident underscores the growing threat of software supply-chain compromises, where routine pip install commands can transform into high-impact security breaches

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Attack Details

• Discovery: Malicious packages flagged on PyPI on August 4, 2025.

• Packages Involved:

  • sisaws: Masqueraded as government API integration utilities, including input validation and timestamped dictionary responses to appear legitimate. Contained a hidden initializer that, when triggered with a token, decoded a hex string to execute a curl command, fetching SilentSync.

  • secmeasure: Appeared to offer string manipulation helpers but included a backdoor that executed the same curl-based delivery chain.

• SilentSync RAT Capabilities:

  • Harvests browser-stored credentials and cookies

  • Executes arbitrary shell commands

  • Captures screenshots and exfiltrates files or directories

  • Removes artifacts to evade detection

  • Communicates with C2 server over plaintext

• Targeted Scope: While current distribution prioritizes Windows, the RAT contains modules for Linux and macOS, making it a cross-platform risk

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Recommendations

• Verify Dependencies Before Install: Double-check PyPI package names, authors, and versions to avoid typosquatting traps like sisaws.

• Use Trusted Packages: Prefer widely used, actively maintained libraries with strong community reputations and documented update histories.

• Automate Dependency Scanning: Integrate security scanning tools into CI/CD pipelines to detect malicious or vulnerable packages early.

• Enhance Endpoint Protection: Deploy NGAV/EDR solutions with ML-based behavioral analysis to catch RAT activity.

• Monitor for Anomalous Network Activity: Inspect development environments for suspicious outbound curl executions and unexpected downloads

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Indicators of Compromise (IoCs)

MD5 Hashes

• 327233d73236ca4d7c18ffd8f9924127

• 9a092bbfc5325cbfca2f9807d074616a

• 3918cace55342909c8309ec37d0207fd

SHA256 Hash

• bbe8f3e78ca09b8deb0d476d45bedc2aa1401916e5de20819d9e745e2b7d3ab0

URL

• hxxps[:]//pastebin[.]com/raw/jaH2uRE1

IPv4

• 200[.]58[.]107[.]25

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MITRE ATT&CK TTPs

• Initial Access: T1195 (Supply Chain Compromise)

• Execution: T1059 (Command and Scripting Interpreter), T1140 (Deobfuscate/Decode Files)

• Persistence: T1547 (Boot or Logon Autostart Execution), T1547.001 (Registry Run Keys/Startup Folder)

• Defense Evasion: T1027 (Obfuscated Files/Information), T1036 (Masquerading), T1106 (Native API)

• Credential Access: T1555 (Credentials from Password Stores), T1555.003 (Credentials from Web Browsers), T1539 (Steal Web Session Cookie)

• Discovery: T1082 (System Information Discovery)

• Collection: T1113 (Screen Capture)

• Exfiltration: T1041 (Exfiltration Over C2 Channel)

• Command & Control: T1071 (Application Layer Protocol)

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References

• Zscaler – Malicious PyPI Packages Deliver SilentSync RAT

• MITRE ATT&CK Techniques

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