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

Static analysis result for SHA-256 ca23210f9fb6e852…

MALICIOUS

Office (OLE) / .XLSX

1.17 MB
MD5: 4e8ece755ac2b0175461c4df0f7ad1c7 SHA-1: be6fde9bfc9ac3d05b2f0d7fbceecceecdd96885 SHA-256: ca23210f9fb6e852316a88f6f13ca97b558b134ac91e7c972dedfd7dcbd06e1c
200 Risk Score

Malware Insights

MITRE ATT&CK
T1204.002 User Execution: Malicious File T1059 Command and Scripting Interpreter T1203 // a bit of a bit of a bit of a bit of a bit of a bit of a bit of a bit of a bit of a bit of a bit of a bit of a bit of T1203 Exploit Public-Facing Application

The sample is a malicious Excel file that employs a default-password encryption (VelvetSweatshop) to evade detection. It contains an Equation Editor OLE object with a malformed Ole10Native stream, which is characteristic of exploits targeting CVE-2017-11882. No scripts were extracted from this sample, but the structural evidence and ClamAV detection as a downloader indicate the intent to execute a payload upon exploitation of the Equation Editor vulnerability.

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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