Formbook Office (OLE) / .XLSX malware analysis — malicious · 8d060e82fec27d68

MALICIOUS

Office (OLE) / .XLSX

162.1 KB First seen: 2022-06-28

MD5: 5a9b4f7d10404153c4d51a189d6ad24f SHA-1: 6e5116ef974411c535b50ba372c1a81e5f471fad SHA-256: 8d060e82fec27d68e88eb996f24c6b890d2f54812390720a747412819cfb08e4

262 Risk Score

Malware Insights

Formbook · confidence 95%

MITRE ATT&CK

T1204.002 Malicious File T1071.001 Web Protocols T1105 Ingress Tool Transfer

The critical heuristic CVE_2017_0199 indicates that this Office document exploits a known vulnerability to load a remote payload from the URL http://blooket.github.io@192.227.168.194/office_dc/invc_17.doc. The ClamAV detection further confirms its malicious nature, identifying it as a Formbook downloader. The document is encrypted, which is a common tactic to evade static analysis and hide malicious content.

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_17.doc

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