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

Static analysis result for SHA-256 bc03e79179795e31…

MALICIOUS

Office (OOXML) / .XLSX

733.3 KB Created: 2022-05-16 17:34:45 UTC Authoring application: Microsoft Excel 16.0300 First seen: 2022-05-27
MD5: 3fed4357a9a31f6d784d90e0e2828cef SHA-1: b10fe00a3142c331aa805a78b5e01e9fa73d9c6b SHA-256: bc03e79179795e31ba88934475f0746f25a7382a157ab005a54cae03b83c797d
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 an Equation Editor object. High-severity 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. ClamAV detection confirms this as a downloader Trojan. The presence of these indicators strongly suggests the file is designed to exploit vulnerabilities within the Equation Editor to download and execute a secondary payload.

Heuristics 4

  • Equation Editor OLE object high CVE related OLE_EQUATION_EDITOR
    Embedded OLE object xl/embeddings/KSkzQJ0.8Z 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
f47c403fe4553bed065eae759c336e9ec9f43fc66bc9efb0a3ac3734685ff063		 ooxml-ole-object OOXML embedded OLE part: xl/embeddings/KSkzQJ0.8Z 874496 bytes
ooxml_oleobject_00_ole10native_00.bin
4ba804f489331c851f24eeaf6870567587ee64cf26d286f4d261b20e110d5790		 ole-package OOXML xl/embeddings/KSkzQJ0.8Z Ole10Native stream: OLe10NAtIvE 864965 bytes
emf_00.emf
38f17a599ac5d645df3840bbb401710ef81573a747da20abbfc1b7d9a9273b58		 ooxml-emf OOXML EMF part: xl/media/image1.emf 169096 bytes

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