Formbook Office (OLE) / .XLSX malware analysis — malicious · ea59c188ea18e6b2

MALICIOUS

Office (OLE) / .XLSX

162.0 KB First seen: 2022-06-29

MD5: 89c42005b7512f455038ba0918a83946 SHA-1: b97124a0ff89e572dc782d7d7a7e0d0f6acabaf3 SHA-256: ea59c188ea18e6b279b0e84a1eb4c6ce55f8b7d1b754f86efd68019cdf7eb20d

262 Risk Score

Malware Insights

Formbook · confidence 95%

MITRE ATT&CK

T1204 Malicious Link T1204.001 Malicious Link: Malicious Link T1059 Command and Scripting Interpreter T1190 Exploit Public-Facing Application

The sample is a password-encrypted Office document that exploits CVE-2017-0199 via an embedded OLE object. This exploit is designed to download and execute a second-stage payload from the URL http://blooket.github.io@192.227.168.194/office_dc/invc_15.doc. ClamAV detection confirms this is a Formbook downloader.

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_15.doc

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