Formbook Office (OOXML) / .XLSX malware analysis — malicious · 40448a4c3c2fb658

MALICIOUS

Office (OOXML) / .XLSX

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

MD5: 601d33bc93c3d67735c254efeacd31a7 SHA-1: 01a95769c8510193497ac1d02e190d1e38b42b63 SHA-256: 40448a4c3c2fb6587b2b68735fab1137fd677d63e3e9806e4b619d0b9f4f38da

210 Risk Score

Malware Insights

Formbook · confidence 95%

MITRE ATT&CK

T1204 Malicious Link T1566 Phishing T1059 Command and Scripting Interpreter

The file contains an embedded Equation Editor OLE object that exhibits anomalies consistent with CVE-2018-0798. ClamAV detection identifies the sample as Formbook, a known downloader. The embedded object likely serves as the initial stage for delivering the Formbook malware.

Heuristics 7

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
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 3

Files carved from inside the sample during analysis.

Filename	Kind	Source	Size
`ooxml_oleobject_00.bin` `186653592d7e9efa10b6a489859151320694055df96ffa7849e52bc14ae02baf`	ooxml-ole-object	OOXML embedded OLE part: xl/embeddings/oleObject1.bin	1896960 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` `530bae1f49ae7650840f48b6dce41cd7d277c811bd2ff8bb84144f1e2c9d3ae1`	ole-package	OOXML xl/embeddings/oleObject1.bin Ole10Native stream: OLe10nATiVe	1879638 bytes
Detection ClamAV: No threats found Obfuscation or payload: likely Carved artifact entropy is 7.99, consistent with packed or encrypted content.
`emf_00.emf` `f94e852a14a6a66dc03af9058a97c333370dcc6011143ff7ca9c3b015b9b80a9`	ooxml-emf	OOXML EMF part: xl/media/image2.emf	1099960 bytes

Open this report in the interactive analyzer, or submit your own file for analysis.