Formbook Office (OLE) / .XLSX malware analysis — malicious · 3d6a5000d24e2467

MALICIOUS

Office (OLE) / .XLSX

162.4 KB First seen: 2022-06-28

MD5: 4327c6d969852b4038c086bd88ecfbce SHA-1: 3d457abf8315569d988d389b1f0b19ef5c4937c2 SHA-256: 3d6a5000d24e246727bdb015cf0d73d8ad44e88a6ab437e66e8752e4198f551f

262 Risk Score

Malware Insights

Formbook · confidence 95%

MITRE ATT&CK

T1204 Malicious Link T1204.002 Malicious Link: Malicious File T1059 Command and Scripting Interpreter T1071 Application Layer Protocol T1071.001 Application Layer Protocol: Web Protocols

The sample is an encrypted Office document that leverages CVE-2017-0199 to load a remote document from the URL http://blooket.github.io@192.227.168.194/office_dc/invc_19.doc. ClamAV detection indicates this is a Formbook downloader, which typically aims to steal information or provide remote access. The encryption and exploit carrier heuristics confirm the malicious intent.

Heuristics 7

OLE2Link / URL Moniker → remote loader — CVE-2017-0199 critical CVE likely CVE_2017_0199

Document contains an embedded OLE link object whose URL Moniker points to a remote URL. When the host file is opened, Office follows the link, downloads the URL, and processes the response based on its Content-Type (HTA -> mshta.exe, RTF → Word, etc.) — the documented CVE-2017-0199 primitive. The URL extension is not a reliable filter; servers can return different payloads to Office's user agent.
Encrypted Office package with CFB FAT corruption critical OLE_ENCRYPTED_AND_MALFORMED

Encrypted-package shape co-occurs with FAT-chain corruption — the documented combined evasion form.
ClamAV: Doc.Downloader.Formbook-bc97c1e0c33c3c93-9951465-0 critical CLAMAV_DETECTION

ClamAV detected this file as malware: Doc.Downloader.Formbook-bc97c1e0c33c3c93-9951465-0
Default-encrypted OOXML exploit carrier layout high OOXML_ENCRYPTED_EXPLOIT_CARRIER_SHAPE

Default-password encrypted OOXML package contains embedded OLE object parts and additional activation/decoy parts. This layout is common in malicious Excel exploit delivery and requires inspecting the decrypted package.
Office document is password-encrypted medium OFFICE_ENCRYPTED_PACKAGE

OLE container holds MS-OFFCRYPTO encrypted package (Standard Encryption (Office 2007, AES)).
Office OOXML encrypted with default VelvetSweatshop password medium OFFICE_DEFAULT_PASSWORD_ENCRYPTED_OOXML

OLE EncryptedPackage decrypts with Excel's built-in VelvetSweatshop password. Office opens this transparently, and malware uses it to hide OOXML exploit parts from scanners that only inspect the outer OLE container.
Embedded URL info EMBEDDED_URL

One or more URLs were extracted from the document. The URL itself is not a detection — see the per-URL labels for which channel (macro, JS, link annotation, document body, ...) reached each URL.

URL http://blooket.github.io@192.227.168.194/office_dc/invc_19.doc

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