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

Static analysis result for SHA-256 9b81530cb5c9ebb5…

MALICIOUS

Office (OLE) / .XLSX

538.0 KB
MD5: 9a0fb8828c2a0f2d8de0208609e72e5f SHA-1: 6570a9e3a644c73c72f042aff56032deb803ddce SHA-256: 9b81530cb5c9ebb5322deb89d23e1a064850c8041a37f9c9c9d6bfdfaf8dfd46
200 Risk Score

Malware Insights

MITRE ATT&CK
T1204 Malicious Link T1059 Command and Scripting Interpreter T1566 Phishing

The file is an encrypted Excel spreadsheet that utilizes an embedded Equation Editor OLE object. High-confidence heuristics indicate this object exploits CVE-2018-0798, a known vulnerability. This exploit is likely used to download and execute a secondary payload, as suggested by the 'Xls.Downloader' ClamAV detection name. The encryption and embedded exploit carrier point towards a malicious document designed for initial compromise.

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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