Office (OOXML) / .XLSX malware analysis — malicious · efbfadbd3551a8df

MALICIOUS

Office (OOXML) / .XLSX

1.22 MB Created: 2006-09-16 00:00:00 UTC Authoring application: Microsoft Excel 12.0000 First seen: 2022-06-02

MD5: b2fb85c9d08412c720b6cb4938373493 SHA-1: 36bba43d68dfc25bd1f49def8a41bda0076c6142 SHA-256: efbfadbd3551a8dfa47f4e9e1c896261ffce0592ff17f147c82faa5b9f3709ea

142 Risk Score

Malware Insights

MITRE ATT&CK

T1204 Malicious Link T1566 Phishing T1204.001 Malicious Link: Malicious File T1566.001 Phishing: Spearphishing Attachment

The file is an Excel spreadsheet containing an embedded OLE object, specifically identified as a malicious Equation Editor object. High-severity heuristics indicate the exploitation of CVE-2018-0798 due to anomalous native stream properties within the Equation Editor object. This object appears to carry a payload, as suggested by the large declared inner size and high entropy of the Ole10Native stream, which is inconsistent with its actual stream size. The embedded artifacts, 'ooxml_oleobject_00.bin' and 'ooxml_oleobject_00_ole10native_00.bin', are direct results of this exploitation.

Heuristics 5

Equation Editor OLE object high CVE related OLE_EQUATION_EDITOR

Embedded OLE object xl/embeddings/0Za8l.hVbxOI contains the Equation Editor CLSID, the legacy component exploited by CVE-2017-11882, CVE-2018-0802, and CVE-2018-0798.
CVE-2018-0798 — anomalous Equation Editor native stream high CVE likely CVE_2018_0798_EQUATION_NATIVE_ANOMALY

Embedded Equation Editor OLE data contains anomalous native stream bytes consistent with a CVE-2018-0798-style Equation Editor exploit. This is treated as likely CVE evidence because the Equation object is malformed and payload-like, but it does not match the exact public matrix-overflow byte signature.
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
Suspicious extracted artifact info EXTRACTED_FILE_STATIC_TRIAGE

One or more files extracted from inside this sample matched static suspicious-content checks such as script obfuscation, encoded payload blobs, packed data, or execution/download terms.

Extracted artifacts 2

Files carved from inside the sample during analysis.

Filename	Kind	Source	Size
`ooxml_oleobject_00.bin` `49becdea92955f7785515bbd749531b40aa4535b0dd3e4f4b5c0ece12e410593`	ooxml-ole-object	OOXML embedded OLE part: xl/embeddings/0Za8l.hVbxOI	1585664 bytes
Detection ClamAV: No threats found Obfuscation or payload: likely Carved artifact entropy is 7.99, consistent with packed or encrypted content.
`ooxml_oleobject_00_ole10native_00.bin` `688b8ccbfc53c5099809b3d6e4fa12eb7503614f8ac067e060556b8858e3ca3e`	ole-package	OOXML xl/embeddings/0Za8l.hVbxOI Ole10Native stream: OLe10naTive	1570576 bytes
Detection ClamAV: No threats found Obfuscation or payload: likely Carved artifact entropy is 7.99, consistent with packed or encrypted content.

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