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

Static analysis result for SHA-256 ff0562e8970447d9…

MALICIOUS

Office (OOXML) / .XLSX

816.5 KB Created: 2022-05-16 17:34:45 UTC Authoring application: Microsoft Excel 16.0300
MD5: c0cad73f3db386b6cdce5a5dad8409a2 SHA-1: 3b689932d15534bc0e91113689894823de7fa923 SHA-256: ff0562e8970447d959291946d06da0bb0a7bae371019d399aadd968f4287c49a
160 Risk Score

Malware Insights

MITRE ATT&CK
T1566.002 Spearphishing Attachment T1204.002 User Execution: Malicious File T1127.001 Code Signing: Trusted User Interface

The file is identified as malicious by ClamAV, specifically as an 'Xls.Downloader.Trojan'. Static analysis reveals an embedded OLE object within an Equation Editor, which is a known technique for delivering malicious payloads. The anomaly in the Ole10Native stream size suggests it contains a packed or obfuscated second-stage payload.

Heuristics 4

  • Equation Editor OLE object high CVE related OLE_EQUATION_EDITOR
    Embedded OLE object xl/embeddings/Y8.tYXsU 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
9c5abdb744a4717b36d5a71920f989891287899a247737db630e6540821cbd4b		 ooxml-ole-object OOXML embedded OLE part: xl/embeddings/Y8.tYXsU 973312 bytes
ooxml_oleobject_00_ole10native_00.bin
d7792448899341064a21124afe46526aec3fc666db5ff90ef0c38fdbcaa38210		 ole-package OOXML xl/embeddings/Y8.tYXsU Ole10Native stream: OLe10nATIVe 963140 bytes
emf_00.emf
38f17a599ac5d645df3840bbb401710ef81573a747da20abbfc1b7d9a9273b58		 ooxml-emf OOXML EMF part: xl/media/image1.emf 169096 bytes

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