Formbook Office (OOXML) / .XLSX malware analysis — malicious · 00bb07e7cee2f8e6

MALICIOUS

Office (OOXML) / .XLSX

2.25 MB Created: 2006-09-16 00:00:00 UTC Authoring application: Microsoft Excel 12.0000

MD5: e4e7ff037eec2fcf23163a19f27d2b5d SHA-1: 3ce6d0a6935f22fddbfc0c20ec5352d3d1374e06 SHA-256: 00bb07e7cee2f8e666e1b12036748e135529d5b14597b4a6043ee093664bc5d6

270 Risk Score

Malware Insights

Formbook · confidence 95%

MITRE ATT&CK

T1204 Malicious Link T1204.002 Malicious Link: Malicious File T1059 Command and Scripting Interpreter

The sample is an Office document containing an embedded OLE object, specifically targeting a vulnerability in the Equation Editor (CVE-2018-0798). This exploit is known to be used by malware like Formbook to download and execute a secondary payload. The ClamAV detection further confirms its malicious nature as a downloader.

Heuristics 8

Equation Editor OLE object high CVE related OLE_EQUATION_EDITOR

Embedded OLE object xl/embeddings/oleObject1.bin 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.
ClamAV: Doc.Downloader.Formbook-bc97c1e0c33c3c93-9951465-0 critical CLAMAV_DETECTION

ClamAV detected this file as malware: Doc.Downloader.Formbook-bc97c1e0c33c3c93-9951465-0
ClamAV detection on extracted artifact critical EXTRACTED_FILE_CLAMAV

ClamAV flagged at least one file extracted from inside this sample. Even when the wrapping document carries no AV detection of its own, a hit on the carved artifact is a strong indicator the sample is a delivery vehicle.
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
Hidden worksheet (hidden) low OOXML_HIDDEN_SHEET

Excel workbook contains 1 hidden sheet(s) — hidden sheets are commonly used to conceal macro code, staging data, or intermediate payload construction
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 4

Files carved from inside the sample during analysis.

Filename	Kind	Source	Size
`ooxml_oleobject_00.bin` `50f8f81257ba2484899b354f12b45230724fcf616dd473722c2112f391181504`	ooxml-ole-object	OOXML embedded OLE part: xl/embeddings/oleObject1.bin	2181632 bytes
Detection ClamAV: No threats found Obfuscation or payload: likely Carved artifact entropy is 7.98, consistent with packed or encrypted content.
`ooxml_oleobject_00_ole10native_00.bin` `305f7803e5d6c7057a988f3ad796356e0790c9d43384ad710b17fe0c6ecbd26c`	ole-package	OOXML xl/embeddings/oleObject1.bin Ole10Native stream: olE10naTIVE	2161811 bytes
Detection ClamAV: No threats found Obfuscation or payload: likely Carved artifact entropy is 7.99, consistent with packed or encrypted content.
`ooxml_oleobject_01.bin` `c74c38684d6e212e72aefb0a86725652928417719176901e6417f38e33c33a23`	ooxml-ole-object	OOXML embedded OLE part: xl/embeddings/Microsoft_Office_Word_Macro-Enabled_Document1.docm	59084 bytes
Detection ClamAV: Doc.Downloader.Formbook-bc97c1e0c33c3c93-9951465-0 Obfuscation or payload: unlikely
`emf_00.emf` `474e87f8c87caf71aa32677edfa5d6a35505795ee32231fa5700b93698953817`	ooxml-emf	OOXML EMF part: xl/media/image2.emf	1099960 bytes

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