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

Static analysis result for SHA-256 9c2529b776fe1f43…

MALICIOUS

Office (OLE) / .XLSX

1.16 MB
MD5: b3c48fa922fc6a96837a3eed4e781f26 SHA-1: f5966258f7fbdc953c40aad1f5a246f3b7d6a222 SHA-256: 9c2529b776fe1f43eb50e5c9148e6c5acd837e703829dfe506299903888834d5
200 Risk Score

Malware Insights

MITRE ATT&CK
T1059.001 Command and Scripting Interpreter T1071.001 Application Layer Compromise T1566.001 Privilege Escalation T1083 System Modification T1071.002 Application Services Introduction

The file's structure, including the default-encrypted OOXML package, the presence of the Equation Editor CLSID (CVE-2017-11882), and the high-entropy Ole10Native stream, strongly indicate an exploit delivery mechanism. The ClamAV detection confirms malicious intent. The file likely downloads and executes a second-stage payload from the embedded OOXML package, exploiting the Equation Editor vulnerability to gain control of the system. The use of a default password further obfuscates the malicious intent.

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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