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

Static analysis result for SHA-256 538a3c34991f6f5d…

MALICIOUS

Office (OLE) / .XLSX

1.15 MB
MD5: 815ce5f171b5b16a12275327d9c0c588 SHA-1: ee8aa332a82ed2d0dac5624ee22018bbe963316a SHA-256: 538a3c34991f6f5d098785d9e953a7c996530f94937b65ebedf331973a0abc2a
200 Risk Score

Malware Insights

MITRE ATT&CK
T1204 Malicious Link T1204.002 Malicious File T1566 Phishing T1566.001 Spearphishing Attachment T1059 Command and Scripting Interpreter

The file is an encrypted XLSX document that contains an embedded Equation Editor OLE object. This object exhibits anomalies suggesting it carries a malicious payload, a common technique for exploiting vulnerabilities like CVE-2017-11882. The ClamAV detection as 'Xls.Downloader' further supports its malicious nature as a downloader. No plaintext document body or scripts were extractable, limiting the understanding of the specific lure.

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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