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

Static analysis result for SHA-256 1b9854c7241ca543…

MALICIOUS

Office (OLE) / .XLSX

1.11 MB
MD5: a61eb0d04d5d774fdffa7055c1a79dc1 SHA-1: 4d0159f8f5e8957685fa291306a883d44982e929 SHA-256: 1b9854c7241ca543cd2c30fcf5d2cd9948da9eca6693430b12fa1d923301f2a9
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 for Privilege Escalation T1071.002 Application Return - Malicious T1071.003 Application Return - Malicious - Exploit

The file utilizes a standard OOXML dropper pattern, employing default-encrypted Office documents and exploiting the Equation Editor OLE object (CVE-2017-11882) to deliver a malicious payload. The presence of a high-entropy Ole10Native stream within the Equation Editor object, combined with ClamAV detection, strongly suggests an attempt to execute arbitrary code. The decrypted OOXML package reveals the presence of exploit carrier parts, indicating a staged delivery mechanism. The file likely downloads and executes a second-stage payload from an embedded location, leveraging the Equation Editor vulnerability for privilege escalation.

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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