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

Static analysis result for SHA-256 0b20638506b6b6ff…

MALICIOUS

Office (OOXML) / .XLSX

816.2 KB Created: 2022-05-16 17:34:45 UTC Authoring application: Microsoft Excel 16.0300 First seen: 2022-11-15
MD5: 694e2a393bec2bc0cd7db106e391fd0a SHA-1: 405a4ee0a93725506ed5f522afaeb7901d5ff9b3 SHA-256: 0b20638506b6b6ffe28564f757d17d41311a1b1887bfbd3a7e0f0e6df21370b8
160 Risk Score

Malware Insights

Xls.Downloader.Trojan · confidence 95%

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

The file is an Excel spreadsheet containing an embedded OLE object, identified as an Equation Editor. This object carries a payload within its Ole10Native stream, indicated by anomalous size and entropy. ClamAV detection confirms this as a downloader trojan, likely leveraging the embedded object to execute a secondary stage.

Heuristics 4

  • Equation Editor OLE object high CVE related OLE_EQUATION_EDITOR
    Embedded OLE object xl/embeddings/3zV.cMW07q 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
c586085751d733c4c49b3436e34fe0d35812f55471fe8001463b2d36c3693c3a		 ooxml-ole-object OOXML embedded OLE part: xl/embeddings/3zV.cMW07q 1014784 bytes
ooxml_oleobject_00_ole10native_00.bin
9acea066f7cd4f70c43727607e68dfa03cb58915624d8cf842aff75ddcc906bf		 ole-package OOXML xl/embeddings/3zV.cMW07q Ole10Native stream: oLE10nATIve 1004292 bytes
emf_00.emf
38f17a599ac5d645df3840bbb401710ef81573a747da20abbfc1b7d9a9273b58		 ooxml-emf OOXML EMF part: xl/media/image1.emf 169096 bytes

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