Malicious RTF / .DOC — malware analysis report

Static analysis result for SHA-256 fb73c93c978351fd…

MALICIOUS

RTF / .DOC

1.60 MB
MD5: 330c6c2b0ca5bdc31ec28cd629145eaa SHA-1: c8f3660896f6e98be48cf87ca6a2108a9d685d50 SHA-256: fb73c93c978351fd70a26b1ddf59214a191e32d1c36bfd0183d7674987572e68
240 Risk Score

Malware Insights

MITRE ATT&CK
T1204.002 Malicious File: User Execution T1559.001 Component Object Model Hijacking T1059.003 Command and Scripting Interpreter: Windows Command Shell

The sample is an RTF document containing an embedded OLE object that exploits the Equation Editor vulnerability (CVE-2017-11882). The presence of `RTF_EQUATION_EDITOR` and `CVE_2017_11882_RELATED` heuristics strongly indicates this exploit. The `RTF_OBJUPDATE` heuristic suggests that the embedded object is designed to be activated automatically, leading to the execution of a second-stage payload. The large amount of hex-encoded data within the OLE object further supports the presence of a hidden payload.

Heuristics 6

  • Equation Editor OLE1 native payload — CVE-2017-11882 related critical CVE related CVE_2017_11882_RELATED
    RTF decodes to an OLE1 Equation.3 embedded object whose native data is large and payload-like, and \objupdate requests automatic activation. This is the delivery shape used by Equation Editor RCE documents such as CVE-2017-11882/CVE-2018-0802, but the malformed MTEF record needed for exact attribution was not recovered.
  • Split hex Equation Editor ProgID + OLE object critical RTF_EQUATION_EDITOR
    RTF embeds the Equation.3 ProgID as hex bytes near OLE object activation and splits the byte stream with whitespace or an ignorable RTF group. This is an Equation Editor OLE activation surface commonly used by CVE-2017-11882 / CVE-2018-0802 exploit documents.
  • \objupdate forces OLE activation high RTF_OBJUPDATE
    RTF contains \objupdate — forces automatic OLE object instantiation when the document is opened, bypassing user interaction. Almost exclusively seen in Equation Editor exploit documents.
  • Large hex data blocks in OLE object high RTF_EXCESSIVE_HEX
    RTF contains ~1660KB of hex-encoded data inside \objdata sections — may hide a payload
  • OLE object data medium RTF_OBJDATA
    RTF contains 2 \objdata section(s) — embedded OLE objects
  • Embedded OLE object medium RTF_OBJEMB
    RTF contains \objemb — embedded OLE object

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
objdata_00_off000000af.bin
6cc569c2a8358385b347e1c80d558831bc9be198721a375ef8d8cec2f4d5313d		 rtf-objdata-decoded RTF \objdata at offset 0xAF 832569 bytes

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