Malicious RTF / .DOC — malware analysis report

Static analysis result for SHA-256 b8a6575edd8072b3…

MALICIOUS

RTF / .DOC

1.69 MB First seen: 2022-03-23
MD5: 3eff42911cda47b2dd66a7c60ddfafcb SHA-1: af0075e2a6f0fd120b833114ea295e01ec43edcb SHA-256: b8a6575edd8072b3a87976448136cc73dfcb72480bfddfaec51565e594b18ae0
240 Risk Score

Malware Insights

MITRE ATT&CK
T1566.001 Spearphishing Attachment T1204.002 Malicious File T1059.003 Windows Command Shell

The file 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_OBJDATA` and `RTF_EXCESSIVE_HEX` rules suggest that a hidden payload is embedded within the OLE object. The `RTF_OBJUPDATE` heuristic indicates that the embedded object is designed to be automatically activated upon opening the document, leading to the execution of the exploit.

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 ~1761KB 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_off00001991.bin
06e02f4faaea3d8a53429172c30942b7731c5ed8964acd89b29fd1eab407abed		 rtf-objdata-decoded RTF \objdata at offset 0x1991 880613 bytes

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