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

Static analysis result for SHA-256 bfdc87c7c9b82cef…

MALICIOUS

Office (OLE) / .XLSX

1.21 MB
MD5: 55531b508e7e163434307d138573435e SHA-1: 2245777e2f71c60668745481435f7e2ecddab3d5 SHA-256: bfdc87c7c9b82cef9ae5e407fc79943f92aa8728ff4396ba50803d257c334341
200 Risk Score

Malware Insights

MITRE ATT&CK
T1204.002 User Execution: Malicious File T1059.001 Command and Scripting Interpreter: PowerShell T1204.001 User Execution: Malicious Link T1204.002 User Execution: Malicious File

The sample is an encrypted OOXML file containing embedded OLE objects. The presence of a high-entropy Ole10Native stream within an Equation Editor object strongly suggests the use of CVE-2017-11882, which is a памяти-corruption vulnerability in the Equation Editor. The ClamAV detection as a 'Downloader' indicates the likely intent is to drop and execute a second-stage payload.

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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