Malicious RTF / .DOC — malware analysis report

Static analysis result for SHA-256 98a9b9fa71a98faa…

MALICIOUS

RTF / .DOC

1.73 MB First seen: 2022-05-17
MD5: 67207d269f7aa301aff2c08aa5c97b31 SHA-1: c51ada4bd39be1c549adb656ec85aae5644aaaf5 SHA-256: 98a9b9fa71a98faa55978bf96da6fec0361bfeac412cf6c29c7a37b3bbeb3295
220 Risk Score

Malware Insights

MITRE ATT&CK
T1566.001 Spearphishing Attachment T1204.002 Malicious File T1059.001 PowerShell

The file is an RTF document that leverages the Equation Editor vulnerability (CVE-2017-11882) via an embedded OLE object. The presence of `RTF_EQUATION_EDITOR` and `CVE_2017_11882_RELATED` heuristics strongly indicates exploitation of this known vulnerability. The `RTF_OBJDATA` and `RTF_EXCESSIVE_HEX` heuristics suggest that a significant payload is hidden within the OLE object, which is likely executed upon opening the document. No scripts were extracted, and the document body was unreadable, but the exploit itself is sufficient to classify the attack pattern.

Heuristics 5

  • 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 ~1811KB 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

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
objdata_00_off00001427.bin
5c6e0ee03c69d89b4d8ce40a53e7b36afacffad1e513d4ffeb6cd7682f9c05a8		 rtf-objdata-decoded RTF \objdata at offset 0x1427 905932 bytes

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