Xls.Downloader.Trojan — Office (OOXML) / .XLSX malware analysis

Static analysis result for SHA-256 5ceecb59adc2aa25…

MALICIOUS

Office (OOXML) / .XLSX

738.5 KB Created: 2022-05-16 17:34:45 UTC Authoring application: Microsoft Excel 16.0300 First seen: 2023-01-24
MD5: 68b07c628356e2c0624498a299d33e65 SHA-1: 30779ba4f04f642608bb689710dcde41567606e8 SHA-256: 5ceecb59adc2aa25379885aab769273c1807f8c92fad27631af5145237e2dfe9
160 Risk Score

Malware Insights

Xls.Downloader.Trojan · confidence 95%

MITRE ATT&CK
T1204 Malicious File T1559 Component Object Model Hijacking T1559.001 Component Object Model Hijacking: COM Hijacking

The file is identified as malicious by ClamAV, specifically as 'Xls.Downloader.Trojan'. Static analysis revealed an embedded OLE object within an Equation Editor, which is a common technique for delivering malicious payloads. The anomaly in the Ole10Native stream size suggests the embedded object is intended to execute further malicious code.

Heuristics 4

  • Equation Editor OLE object high CVE related OLE_EQUATION_EDITOR
    Embedded OLE object xl/embeddings/FyNu.en 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
c860b63aecfdfc424bca538fc6c26138f5cda2d692e66894bf283ff040e5fce5		 ooxml-ole-object OOXML embedded OLE part: xl/embeddings/FyNu.en 871424 bytes
ooxml_oleobject_00_ole10native_00.bin
efafbff55be0ade72a6760b51741e012c37fc4a4aafe4888671174b3b5213beb		 ole-package OOXML xl/embeddings/FyNu.en Ole10Native stream: olE10NAtIVE 861765 bytes
emf_00.emf
38f17a599ac5d645df3840bbb401710ef81573a747da20abbfc1b7d9a9273b58		 ooxml-emf OOXML EMF part: xl/media/image1.emf 169096 bytes

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