Malicious RTF — malware analysis report

Static analysis result for SHA-256 e57e5321423c3ce7…

MALICIOUS

RTF

1.39 MB First seen: 2021-06-30
MD5: 623fb97e42a3e4303114a0b8407ffe0a SHA-1: 625ebfff2dac65045a06fe70f24b7a1d6ee6667d SHA-256: e57e5321423c3ce785654245da790590e121ff3eeaa4c14b991810d1e40e2589
180 Risk Score

Malware Insights

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

The RTF file contains multiple indicators of exploitation, specifically related to OLE object embedding and activation, and a critical heuristic firing for CVE-2017-11882. The presence of ` tf_equation_editor` and ` tf_objupdate` strongly suggests the exploitation of the Equation Editor vulnerability to trigger OLE object activation. This is a common method for delivering secondary payloads.

Heuristics 5

  • Split hex Equation Editor ProgID + OLE object critical CVE likely 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.
  • 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.
  • \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_off000011e1.bin rtf-objdata-decoded RTF \objdata at offset 0x11E1 53347 bytes
SHA-256: e65be7d8f4a76dc5b3c8d7c4fc503f1b5eccc889299562094044677fb5231d24
objdata_01_off0002ed17.bin rtf-objdata-decoded RTF \objdata at offset 0x2ED17 346025 bytes
SHA-256: 5d913e0bdd4543b59117490fda1dba3c38edbcd2b81c5376d07402a696f7c2ab

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