Formbook — Office (OLE) / .XLSX malware analysis

Static analysis result for SHA-256 08787bae1fd03302…

MALICIOUS

Office (OLE) / .XLSX

186.0 KB First seen: 2022-03-21
MD5: c2a05210e59b0959313f0dbb2dc59ee2 SHA-1: dc147fbb3098e5b1f5fdd40bc6ebe7e2468b7fbb SHA-256: 08787bae1fd0330260930f2d08c3830ecce86198cbb2e87557fa71d2ae1db430
240 Risk Score

Malware Insights

Formbook · confidence 95%

MITRE ATT&CK
T1566.001 Spearphishing Attachment T1203 Exploitation for Client Execution

The file is a password-encrypted OOXML document identified as a malicious downloader by ClamAV, specifically detecting the Formbook family. It contains an embedded Equation Editor OLE object, a common vector for exploiting vulnerabilities like CVE-2017-11882. The encryption and malformed structure indicate an attempt to evade static analysis, with the embedded OLE object likely serving as the exploit carrier.

Heuristics 6

  • Equation Editor OLE object high CVE related OLE_EQUATION_EDITOR
    Default-encrypted OOXML 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.
  • 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.