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

Static analysis result for SHA-256 4da7c61ec6eb7520…

MALICIOUS

Office (OLE) / .XLSX

540.7 KB
MD5: aaaa1eefa79498a5f6e5fe8940827962 SHA-1: 27031645bd8e3dc666d6de7c7bf4ef01779d354f SHA-256: 4da7c61ec6eb75209eb168ec610d851389a01c06975a6236de3729328fdcc450
200 Risk Score

Malware Insights

MITRE ATT&CK
T1059.001 Command and Scripting Interpreter T1071.001 Application Layer Compromise

The file utilizes a standard OOXML dropper pattern, employing default-encrypted OLE objects and exploiting the Equation Editor component (CVE-2018-0798) to conceal a malicious payload. The presence of the anomalous Equation Editor native stream and the ClamAV detection strongly indicate a downloader attempting to execute a payload. The decryption of the OOXML package reveals the presence of exploit parts, further supporting this assessment. The file likely downloads and executes a second-stage payload from a remote location.

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.
  • CVE-2018-0798 — anomalous Equation Editor native stream high CVE likely CVE_2018_0798_EQUATION_NATIVE_ANOMALY
    Default-encrypted OOXML contains embedded Equation Editor data with anomalous native stream bytes consistent with a CVE-2018-0798-style exploit. This is treated as likely CVE evidence because the Equation object is malformed and payload-like.
  • 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.
  • 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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