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

Static analysis result for SHA-256 31f9982b2c0c9cc9…

MALICIOUS

Office (OLE) / .XLSX

1.23 MB
MD5: f726147c96d9766c17b636ee1572b48c SHA-1: 9c91561c0046f18ef885fce32e599126852c1c1d SHA-256: 31f9982b2c0c9cc9017882eeaec57e7756aa0e9e4414a1483cf8fc72860f78dd
140 Risk Score

Malware Insights

MITRE ATT&CK
T1566.001 Spearphishing Attachment T1204.002 Malicious File

The sample is an encrypted Office XLSX file. High-severity heuristics indicate it contains an Equation Editor OLE object (OLE_EQUATION_EDITOR) which is anomalous and carries a payload-like stream (OLE_EQUATION_OLE10NATIVE_PAYLOAD_ANOMALY). This strongly suggests the file is designed as an exploit carrier, likely leveraging a known Equation Editor vulnerability. The default password encryption (OFFICE_DEFAULT_PASSWORD_ENCRYPTED_OOXML) is a common technique to hinder initial analysis.

Heuristics 4

  • 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.
  • 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.