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

Static analysis result for SHA-256 7760c915290bd5d0…

MALICIOUS

Office (OOXML) / .XLSX

789.7 KB Created: 2022-05-16 17:34:45 UTC Authoring application: Microsoft Excel 16.0300 First seen: 2022-06-07
MD5: cada5d58fa7be51829da4faf8b9ac884 SHA-1: d8df761a3493c350de614250feb137368c5cac5d SHA-256: 7760c915290bd5d04dbb1cf660a11e2ee52b15575ce08482d1bc2061810344cb
160 Risk Score

Malware Insights

Xls.Downloader.Trojan · confidence 95%

MITRE ATT&CK
T1566.001 Spearphishing Attachment T1203 Exploitation for Client Execution

The sample is an Excel document containing an embedded Equation Editor OLE object. This object's Ole10Native stream has an anomalous size and entropy, strongly indicating it contains a malicious payload. ClamAV detection confirms this, identifying it as Xls.Downloader.Trojan. The embedded object is likely used to execute a secondary payload upon opening.

Heuristics 4

  • Equation Editor OLE object high CVE related OLE_EQUATION_EDITOR
    Embedded OLE object xl/embeddings/glnnd6.52KjelD 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
6c5f77cd095ed4def7bc60b57211505454287a6eeb3d585b311b944515961530		 ooxml-ole-object OOXML embedded OLE part: xl/embeddings/glnnd6.52KjelD 904192 bytes
ooxml_oleobject_00_ole10native_00.bin
60e6f09f32fb82b565d6b91ac93490656c5cbbadf49a5b10353391fed228fcff		 ole-package OOXML xl/embeddings/glnnd6.52KjelD Ole10Native stream: OlE10nativE 894714 bytes
emf_00.emf
38f17a599ac5d645df3840bbb401710ef81573a747da20abbfc1b7d9a9273b58		 ooxml-emf OOXML EMF part: xl/media/image1.emf 169096 bytes

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