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

Static analysis result for SHA-256 0931d1c5ba3b0b9a…

MALICIOUS

Office (OOXML) / .XLSX

727.3 KB Created: 2022-05-16 17:34:45 UTC Authoring application: Microsoft Excel 16.0300 First seen: 2022-11-30
MD5: faf48e0107d58d850753b44ac6eee6ed SHA-1: 3b0c1458276857c915d3187fa91ad7f2f4e77f34 SHA-256: 0931d1c5ba3b0b9ad7c7c492c569f111f01c66ba2f16ed81de144fa39bf35574
160 Risk Score

Malware Insights

Xls.Downloader.Trojan · confidence 95%

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

The sample is an Excel spreadsheet containing an embedded OLE object, identified as an Equation Editor. This object exhibits anomalies in its Ole10Native stream, suggesting it carries a malicious payload. ClamAV detection confirms this, classifying it as Xls.Downloader.Trojan. The presence of these indicators strongly suggests a malicious downloader attempting to execute further stages.

Heuristics 4

  • Equation Editor OLE object high CVE related OLE_EQUATION_EDITOR
    Embedded OLE object xl/embeddings/B5hUB.iizbom 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
b84bed349e5e7ca2176f78d5ef4e33d0e0d18b6fea55a6474e75d7a0de19c575		 ooxml-ole-object OOXML embedded OLE part: xl/embeddings/B5hUB.iizbom 873472 bytes
ooxml_oleobject_00_ole10native_00.bin
933b030826f6617278e8b0de813afed4fb859d0437954ebb6e7e6ea0bc8af180		 ole-package OOXML xl/embeddings/B5hUB.iizbom Ole10Native stream: OlE10NativE 863822 bytes
emf_00.emf
38f17a599ac5d645df3840bbb401710ef81573a747da20abbfc1b7d9a9273b58		 ooxml-emf OOXML EMF part: xl/media/image1.emf 169096 bytes

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