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

Static analysis result for SHA-256 d6d6d06f132571ed…

MALICIOUS

Office (OLE) / .XLSX

1.21 MB
MD5: 87d51f73e7de9c7984b763edf43f0048 SHA-1: 7067fa9712c4c9c8c7c63d94db2a08f6fbfc7b30 SHA-256: d6d6d06f132571ed737c1977849faf2e199cf1478d22346cd0edd1fca95aeac9
200 Risk Score

Malware Insights

MITRE ATT&CK
T1203 Exploitation for Client Execution T1566.001 Phishing: Spearphishing Attachment T1027 Obfuscated Files or Information

The sample is an Excel file encrypted with the default 'VelvetSweatshop' password to evade detection. It contains an embedded OLE object with the Equation Editor CLSID and a malformed Ole10Native stream, which is characteristic of Equation Editor exploits (CVE-2017-11882). The ClamAV detection as a downloader indicates the likely intent is to fetch and execute a second-stage payload after successful exploitation.

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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