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

Static analysis result for SHA-256 e302eed2966ae459…

MALICIOUS

Office (OLE) / .XLSX

1.24 MB
MD5: 1de397d83bd488f77512be7139e8ded7 SHA-1: 3b380e17542a8c3a00fd116ec7bbc750c40fea7a SHA-256: e302eed2966ae4596d1205328487680c0ee8e9692434e1fb5695c09b6fa2f852
200 Risk Score

Malware Insights

MITRE ATT&CK
T1204.002 User Execution: Malicious File T1059 Command and Scripting Interpreter T1203 Exploitation for Client Execution

The sample is an encrypted XLSX file using a default password, which is a common technique to bypass static analysis. It contains an embedded Equation Editor OLE object with a payload-like Ole10Native stream, indicating an exploit for CVE-2017-11882 or similar. The ClamAV detection specifically identifies it as a downloader, suggesting the second-stage payload is likely to be executed upon successful 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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