Malicious RTF / .DOC — malware analysis report

Static analysis result for SHA-256 42fddd0c48879242…

MALICIOUS

RTF / .DOC

1.73 MB First seen: 2022-05-11
MD5: a38802a6634224f5f78fb4371fa279b3 SHA-1: 666d4ad02515a52d2979ec98687070795872786e SHA-256: 42fddd0c48879242ca31ff29ae52aa4cfb168e7876d9d90516b0e3deb9349cf3
180 Risk Score

Malware Insights

MITRE ATT&CK
T1566.001 Spearphishing Attachment T1204.002 Malicious File

The file is an RTF document containing an embedded OLE object that leverages the Equation Editor vulnerability (CVE-2017-11882). The `RTF_EQUATION_EDITOR` and `CVE_2017_11882_ACTIVATION_RELATED` heuristics confirm this. The `RTF_OBJUPDATE` heuristic indicates that the OLE object is forced to activate, likely leading to the execution of a secondary payload. The document body contains obfuscated VBA-like code, suggesting the embedded object is designed to run malicious scripts.

Heuristics 5

  • Equation Editor activation — CVE-2017-11882 related high CVE related CVE_2017_11882_ACTIVATION_RELATED
    RTF decodes to an Equation.3 ProgID and requests OLE activation with \objemb plus \objupdate. This reaches the legacy Equation Editor attack surface used by CVE-2017-11882/CVE-2018-0802 documents, but the malformed MTEF/native payload needed for stronger 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.
  • 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 2

Files carved from inside the sample during analysis.

FilenameKindSourceSize
objdata_00_off000012ab.bin
b8af34e4c36380a6613b5ea189d1c6ec919f3655a88bd48cbff1558b98e6837d		 rtf-objdata-decoded RTF \objdata at offset 0x12AB 154441 bytes
objdata_01_off000582ac.bin
c6836530895d3068b0bd13b6673e20cfb3c2472da47cd4c3fb2419898144731b		 rtf-objdata-decoded RTF \objdata at offset 0x582AC 345132 bytes

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