Malicious RTF / .DOC — malware analysis report

Static analysis result for SHA-256 218be6350f611346…

MALICIOUS

RTF / .DOC

2.06 MB First seen: 2022-04-12
MD5: 3200ce697a537c4e866a29102f4ce606 SHA-1: 32daaab0fdc7f57cc4683cc7953ce34ce8773fb7 SHA-256: 218be6350f6113463a0d1206589de050eac190a6ae5493e649413dff62ad19db
240 Risk Score

Malware Insights

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

The RTF file contains embedded OLE objects and specifically triggers the CVE-2017-11882 vulnerability related to Equation Editor. This exploit is known to be used for delivering second-stage payloads. The presence of `RTF_EQUATION_EDITOR` and `CVE_2017_11882_RELATED` heuristics strongly indicates this attack vector. The large amount of hex-encoded data within the OLE object suggests it is used to hide the malicious 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 ~2149KB 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_off000018ae.bin
fa936083d3ede2af470baa1f62fbee0a95a1e14ccf326fdfa39e54e6cbcd94fa		 rtf-objdata-decoded RTF \objdata at offset 0x18AE 1074951 bytes

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