Formbook Office (OOXML) / .XLSX malware analysis — malicious · 117e50c532ad9637

MALICIOUS

Office (OOXML) / .XLSX

416.7 KB Created: 2006-09-16 00:00:00 UTC Authoring application: Microsoft Excel 12.0000

MD5: 398f1b271481b53f5c49971291db6a9a SHA-1: 1468c2d2c4a7c0f1338d7db1b6f69dcf803e1922 SHA-256: 117e50c532ad963720cb3fdef614dd5792eaca07546612e8248b3b7fc978ec83

270 Risk Score

Malware Insights

Formbook · confidence 95%

MITRE ATT&CK

T1203 Exploitation for Client Execution T1566.001 Spearphishing Attachment

The sample is an Excel document containing an embedded OLE object, specifically an Equation Editor object. Heuristics indicate exploitation of CVE-2018-0798, which is known to be used for delivering malware. ClamAV detections confirm this, identifying the sample as a downloader for the Formbook family. The embedded OLE object likely contains shellcode that exploits the Equation Editor vulnerability to download and execute a secondary payload.

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` `4cbdf71c6afb56a76745a0f0e1cc8b5043247ef74185ebe535b92ddf13af7ad7`	ooxml-ole-object	OOXML embedded OLE part: xl/embeddings/oleObject1.bin	237056 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` `a6706157e4c0b978486e143013aace20d5b3eb4d7975000fa0b19453d6780a90`	ole-package	OOXML xl/embeddings/oleObject1.bin Ole10Native stream: OlE10NatIVE	232919 bytes
Detection ClamAV: No threats found Obfuscation or payload: likely Carved artifact entropy is 8.00, consistent with packed or encrypted content.
`ooxml_oleobject_01.bin` `8b0e4731995bbaa96ad2a3efc998114fc9ad6960d5d211d4d6661ac4507f0607`	ooxml-ole-object	OOXML embedded OLE part: xl/embeddings/Microsoft_Office_Word_Macro-Enabled_Document1.docm	59090 bytes
Detection ClamAV: Doc.Downloader.Formbook-bc97c1e0c33c3c93-9951465-0 Obfuscation or payload: unlikely
`emf_00.emf` `69974e1f41978a38f6118a09eefeacd1f43aacbfe253fdf532b51c632b9d2045`	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.