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

Static analysis result for SHA-256 43ddafd6589dd3eb…

MALICIOUS

Office (OOXML) / .XLSX

790.1 KB Created: 2022-05-16 17:34:45 UTC Authoring application: Microsoft Excel 16.0300 First seen: 2022-07-18
MD5: 68e0cc7e7704565daac52ddc7a9599c9 SHA-1: 638165ced33a2f3ee78dfd783cdbefbbc2b9a3a8 SHA-256: 43ddafd6589dd3ebe06f7dc210c4985a65a19439e1abd523bac34f8c4e2d59e2
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. This object carries a payload-like stream with an anomalous header, strongly indicating it's used for malicious purposes. ClamAV detection confirms this, identifying it as Xls.Downloader.Trojan. The embedded object likely serves to download and execute a second-stage payload.

Heuristics 4

  • Equation Editor OLE object high CVE related OLE_EQUATION_EDITOR
    Embedded OLE object xl/embeddings/ws.cOEdLP 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
35f3de0ddc7f36f19d423a2a49906777f50ec83e21ac8aa1d517fc75bee2c854		 ooxml-ole-object OOXML embedded OLE part: xl/embeddings/ws.cOEdLP 952832 bytes
ooxml_oleobject_00_ole10native_00.bin
74fadcd830bbd099b4e13580a442baf47a3978a4f1e0d808f57e189226dbe612		 ole-package OOXML xl/embeddings/ws.cOEdLP Ole10Native stream: OLe10NAtivE 942912 bytes
emf_00.emf
38f17a599ac5d645df3840bbb401710ef81573a747da20abbfc1b7d9a9273b58		 ooxml-emf OOXML EMF part: xl/media/image1.emf 169096 bytes

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