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

Static analysis result for SHA-256 4f7b8c29006ef834…

MALICIOUS

Office (OLE) / .XLSX

1.10 MB
MD5: 7333160e223353c997358d1e7fc689d5 SHA-1: 0a1f31197b3b50b06d9fc5271133d5d489e0fce5 SHA-256: 4f7b8c29006ef83433912fc5e138c4c970d8a70fae33dd7a73647606ffbd0579
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 a default-password encrypted Excel file containing embedded OLE objects with the Equation Editor CLSID. The presence of a malformed Ole10Native stream within the Equation Editor object strongly indicates an exploit payload for CVE-2017-11882 or similar Equation Editor vulnerabilities. No scripts were extracted from this sample, but the ClamAV detection as a downloader suggests the subsequent stage of the execution chain is a payload delivery mechanism.

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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