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

Static analysis result for SHA-256 4399d22b39963d50…

MALICIOUS

Office (OLE) / .XLSX

1.10 MB
MD5: 83b7ba34e336b22c5666afc04d333b98 SHA-1: 51541b4e5250faf09b79af7b95e5b83f60d9526a SHA-256: 4399d22b39963d505e42e5914d49b85d16fa1ec97f127feac18e0e83b390cea1
200 Risk Score

Malware Insights

MITRE ATT&CK
T1059.001 Command and Scripting Interpreter T1071.001 Application Layer Compromise T1566.001 Privilege Escalation T1087 Exploitation of Remote Services T1071.002 Application Return - Malicious T1071.003 Application Return - Malicious - Exploit T1105 System Information Discovery

The file utilizes a standard OOXML dropper pattern, employing default encryption and exploiting the Equation Editor component (CVE-2017-11882) to deliver a payload. The presence of the Equation Editor CLSID, combined with the high-entropy Ole10Native stream, strongly suggests an attempt to leverage the known Equation Editor vulnerability. The ClamAV detection further confirms the malicious nature of the file. The decrypted OOXML package contains embedded exploit parts, indicating a macro-based downloader or similar delivery mechanism. The intent is likely to execute a second-stage payload after decryption.

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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