Formbook — Office (OLE) / .XLSX malware analysis

Static analysis result for SHA-256 0ce81f8966c50629…

MALICIOUS

Office (OLE) / .XLSX

186.4 KB First seen: 2022-03-16
MD5: 3d921c91217cdd2d7211a436aa939c77 SHA-1: 302e950c8d331b8a950489c7183ae50f22406a29 SHA-256: 0ce81f8966c506292d9b24dc4219910f7309f9a6b59d2b7bc89c3ec5fc46850e
240 Risk Score

Malware Insights

Formbook · confidence 95%

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

The sample is a password-encrypted Office document identified by ClamAV as Doc.Downloader.Formbook. It contains an embedded Equation Editor OLE object, a common technique for exploiting vulnerabilities to execute arbitrary code. The encryption and malformed structure suggest an attempt to evade static analysis, with the embedded 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.