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

Static analysis result for SHA-256 6cf5eb81d932e600…

MALICIOUS

Office (OOXML) / .XLSX

832.9 KB Created: 2022-05-16 17:34:45 UTC Authoring application: Microsoft Excel 16.0300 First seen: 2023-07-18
MD5: ed0f6b9c5a0dc40bbc6ca735b598f3e2 SHA-1: ed759b9b984748146933834be8ad9e987fd3312f SHA-256: 6cf5eb81d932e600c8ca6662cdd81fad871d2a31733a39154862062782d1a58b
160 Risk Score

Malware Insights

MITRE ATT&CK
T1566.002 Spearphishing Attachment T1204.002 Malicious File

The file is an Excel document containing an embedded OLE object, specifically identified as an Equation Editor object. Heuristics indicate that this Equation Editor object carries a payload-like Ole10Native stream with an anomalous size and entropy, strongly suggesting it's a dropper. ClamAV detection confirms this as a downloader trojan. The primary attack vector is likely spearphishing, leveraging the Equation Editor vulnerability to execute the embedded payload.

Heuristics 4

  • Equation Editor OLE object high CVE related OLE_EQUATION_EDITOR
    Embedded OLE object xl/embeddings/A3CIcIyn.1WDhwpI contains the Equation Editor CLSID, the legacy component exploited by CVE-2017-11882, CVE-2018-0802, and CVE-2018-0798.
  • ClamAV: Xls.Downloader.Trojan-aa0b8f388d8573cd-aa0b8f388d8573cd-9950439-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Xls.Downloader.Trojan-aa0b8f388d8573cd-aa0b8f388d8573cd-9950439-0
  • Equation Editor object carries payload-like Ole10Native stream high OLE_EQUATION_OLE10NATIVE_PAYLOAD_ANOMALY
    Embedded OLE object declares the Equation Editor CLSID but stores a large high-entropy Ole10Native stream with malformed package sizing. This is an exploit-shaped Equation/OLE payload container seen in malicious OOXML samples. It is not assigned to a specific CVE unless the MTEF/Equation Native primitive also matches.
  • Embedded OLE object medium OOXML_OLE_OBJECT
    Document contains an embedded OLE object

Extracted artifacts 3

Files carved from inside the sample during analysis.

FilenameKindSourceSize
ooxml_oleobject_00.bin
6ef379780b2b5f73c81fca9ce2095dd9a0b05e468456f5dfee1bcfcc265ad100		 ooxml-ole-object OOXML embedded OLE part: xl/embeddings/A3CIcIyn.1WDhwpI 986624 bytes
ooxml_oleobject_00_ole10native_00.bin
3335a89ce8f3f2b924bddb98349a86b4a93ed52385a92808deb829a3b3728516		 ole-package OOXML xl/embeddings/A3CIcIyn.1WDhwpI Ole10Native stream: oLE10nATiVE 975973 bytes
emf_00.emf
38f17a599ac5d645df3840bbb401710ef81573a747da20abbfc1b7d9a9273b58		 ooxml-emf OOXML EMF part: xl/media/image1.emf 169096 bytes

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