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

Static analysis result for SHA-256 7ef7fb9a4c66c7ba…

MALICIOUS

Office (OLE) / .XLSX

1.17 MB
MD5: d15872e94e5148e2186ec70ac5d6971d SHA-1: 3b4e3e5e79548c06a029a8d796b2c3b2ae682ce2 SHA-256: 7ef7fb9a4c66c7baf6b4ad158ff19fa496e7bfc4ed9d98c920054016c00b6cdd
200 Risk Score

Malware Insights

MITRE ATT&CK
T1059.001 Command and Scripting Interpreter T1071.001 Application Layer Compromise T1566.001 Privilege Escalation T1071.002 Remote Services - SMB/Windows T1105 System Information Discovery

The file's structure and heuristic detections strongly indicate a malicious Excel document designed to deliver a downloader. The use of a default-encrypted OOXML package, combined with the Equation Editor OLE object containing a large, high-entropy stream, is a classic technique for concealing malicious code and exploiting CVE-2017-11882. The ClamAV detection confirms the presence of known malware. The file likely downloads and executes a second-stage payload from a remote URL, establishing a connection to a command-and-control server. The Equation Editor component is a key indicator of this attack.

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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