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

Static analysis result for SHA-256 b11e6926034ac7a3…

MALICIOUS

Office (OOXML) / .XLSX

880.2 KB Created: 2022-05-16 17:34:45 UTC Authoring application: Microsoft Excel 16.0300 First seen: 2023-10-12
MD5: e595c84a07720e172cf6ee067de79139 SHA-1: 98466134fb2ab4dad396a568140beec9a9e505b6 SHA-256: b11e6926034ac7a3a40a4e3b34a1452c5d799138ce314b9914a30817fe1a983f
160 Risk Score

Malware Insights

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

The sample is an Excel file containing an embedded OLE object, specifically identified as a Microsoft Equation Editor object. Heuristics indicate that this Equation Editor object carries a payload-like Ole10Native stream with an anomalous header and size, strongly suggesting exploitation of a vulnerability within the Equation Editor. ClamAV detection confirms this as a downloader trojan.

Heuristics 4

  • Equation Editor OLE object high CVE related OLE_EQUATION_EDITOR
    Embedded OLE object xl/embeddings/XEX.z3jJ7 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
b5e39fc71a60873b8f8d498b28ecf74743778ff61da10058f4945f7a733e4148		 ooxml-ole-object OOXML embedded OLE part: xl/embeddings/XEX.z3jJ7 1073152 bytes
ooxml_oleobject_00_ole10native_00.bin
4e71fd23a8e366adff9601d421a302891b2fb83b5c1cf3885c0d95dd0d367a50		 ole-package OOXML xl/embeddings/XEX.z3jJ7 Ole10Native stream: OLE10nAtIvE 1062111 bytes
emf_00.emf
38f17a599ac5d645df3840bbb401710ef81573a747da20abbfc1b7d9a9273b58		 ooxml-emf OOXML EMF part: xl/media/image1.emf 169096 bytes

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