Malicious Office (OOXML) / .XLSX — malware analysis report

Static analysis result for SHA-256 aa2dc6551f70aa30…

MALICIOUS

Office (OOXML) / .XLSX

795.4 KB Created: 2022-05-16 17:34:45 UTC Authoring application: Microsoft Excel 16.0300 First seen: 2022-08-02
MD5: 743e35fc18b7a9336ef9036adebb3097 SHA-1: ad5ce61816f348f693ed3fd0a20b114b53077ea8 SHA-256: aa2dc6551f70aa300b5d64205532d27bf3988c4c1163ec80ecae635a9c17d5e0
160 Risk Score

Malware Insights

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

The sample is an Excel file containing an embedded OLE object, specifically identified as a Microsoft Equation Editor object. Heuristics indicate that this Equation Editor object carries a payload-like Ole10Native stream with an anomalous header and a significantly larger declared inner size than the actual stream size, strongly suggesting exploitation. ClamAV detection confirms this as a downloader trojan.

Heuristics 4

  • Equation Editor OLE object high CVE related OLE_EQUATION_EDITOR
    Embedded OLE object xl/embeddings/Xfva.u6W 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
4d2a35ed81547ec2af55be1232ac44fefc31545947049cee1a0794e14addd82d		 ooxml-ole-object OOXML embedded OLE part: xl/embeddings/Xfva.u6W 952832 bytes
ooxml_oleobject_00_ole10native_00.bin
6999491332765e1951fbb292cba13a010f401c0ebdf60dbe63d417b663d41666		 ole-package OOXML xl/embeddings/Xfva.u6W Ole10Native stream: OlE10NATIve 942957 bytes
emf_00.emf
38f17a599ac5d645df3840bbb401710ef81573a747da20abbfc1b7d9a9273b58		 ooxml-emf OOXML EMF part: xl/media/image1.emf 169096 bytes

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