Malicious Office (OLE) / .XLSX — malware analysis report

Static analysis result for SHA-256 1c14b383ffd2cde6…

MALICIOUS

Office (OLE) / .XLSX

1.24 MB
MD5: 7c7415819d87cc6c43793218cfced748 SHA-1: 4637673da8e50fc8be9a165eccc5134f20c2c55d SHA-256: 1c14b383ffd2cde64c3cb3481da28d30514c0e8a1ed4c89b2eb5b39fb923814a
200 Risk Score

Malware Insights

MITRE ATT&CK
T1204.002 User Execution: Malicious File T1059.001 Command and Scripting Interpreter: PowerShell T1203 Exploit Public-Facing Application T1203 Exploit Public-Facing Application

The sample is an encrypted Office document utilizing the default VelvetSweatshop password for encryption. It contains Equation Editor OLE objects (xl/embeddings/oleObject1.bin) that exhibit payload-like anomalies in the Ole10Native stream, characteristic of CVE-2017-11882. The ClamAV detection for Xls.Downloader suggests the a payload is intended to download and execute a second-stage malware.

Heuristics 5

  • Equation Editor OLE object high CVE related OLE_EQUATION_EDITOR
    Default-encrypted OOXML embedded OLE object xl/embeddings/oleObject1.bin contains the Equation Editor CLSID, the legacy component exploited by CVE-2017-11882, CVE-2018-0802, and CVE-2018-0798.
  • ClamAV: Xls.Downloader.af2fa5c5d0587870-9978799-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Xls.Downloader.af2fa5c5d0587870-9978799-0
  • Default-encrypted OOXML exploit carrier layout high OOXML_ENCRYPTED_EXPLOIT_CARRIER_SHAPE
    Default-password encrypted OOXML package contains embedded OLE object parts and additional activation/decoy parts. This layout is common in malicious Excel exploit delivery and requires inspecting the decrypted package.
  • Equation Editor object carries payload-like Ole10Native stream high OLE_EQUATION_OLE10NATIVE_PAYLOAD_ANOMALY
    Default-encrypted OOXML embedded OLE object declares the Equation Editor CLSID but stores a large high-entropy Ole10Native stream with malformed package sizing. This is exploit-shaped Equation/OLE payload evidence.
  • Office OOXML encrypted with default VelvetSweatshop password medium OFFICE_DEFAULT_PASSWORD_ENCRYPTED_OOXML
    OLE EncryptedPackage decrypts with Excel's built-in VelvetSweatshop password. Office opens this transparently, and malware uses it to hide OOXML exploit parts from scanners that only inspect the outer OLE container.

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