Xls.Downloader.Trojan-aa0b8f388d8573cd — Office (OOXML) / .XLSX malware analysis

Static analysis result for SHA-256 c99dd5534b0e3916…

MALICIOUS

Office (OOXML) / .XLSX

869.2 KB Created: 2022-05-16 17:34:45 UTC Authoring application: Microsoft Excel 16.0300 First seen: 2023-07-18
MD5: ea1faf5523c76af6706f84401b9809c0 SHA-1: 3853fd3ecd73ad6a419211d257fe9b92be8f58a7 SHA-256: c99dd5534b0e39167b1e995ab122665560815fa208ae07450564d82cc7b46860
160 Risk Score

Malware Insights

Xls.Downloader.Trojan-aa0b8f388d8573cd · confidence 95%

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

The sample is an Excel file containing an embedded Equation Editor OLE object. This object exhibits anomalies in its Ole10Native stream size, strongly indicating it carries a malicious payload. ClamAV detection confirms this, identifying it as Xls.Downloader.Trojan-aa0b8f388d8573cd. The presence of these embedded objects is a common technique for delivering secondary malware.

Heuristics 4

  • Equation Editor OLE object high CVE related OLE_EQUATION_EDITOR
    Embedded OLE object xl/embeddings/ht.BW 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
5501d6d7ed422f5e3ba8598f6225bed172cfc7a93ba711aa5c76d9581b03d032		 ooxml-ole-object OOXML embedded OLE part: xl/embeddings/ht.BW 1077248 bytes
ooxml_oleobject_00_ole10native_00.bin
fc4952ec0fd1e1d96a80a99f7ea69ba97a43a1b3278361e91521c82f99c43f3f		 ole-package OOXML xl/embeddings/ht.BW Ole10Native stream: oLe10NaTIve 1066159 bytes
emf_00.emf
38f17a599ac5d645df3840bbb401710ef81573a747da20abbfc1b7d9a9273b58		 ooxml-emf OOXML EMF part: xl/media/image1.emf 169096 bytes

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