Malicious RTF / .DOC — malware analysis report

Static analysis result for SHA-256 65093c1268405cb2…

MALICIOUS

RTF / .DOC

7.6 KB First seen: 2022-12-08
MD5: 7155f50b87c290ccbcf453fe548d2b94 SHA-1: 8cbffea26fc6b477d7ed938204546e4ec210a240 SHA-256: 65093c1268405cb2b3f623d584070092ddf4d94fb447ab54265df0bac4a1bce9
220 Risk Score

Malware Insights

MITRE ATT&CK
T1566.001 Spearphishing Attachment T1204.002 User Execution: Malicious File T1059.005 Visual Basic

The sample is an RTF document containing an embedded OLE object that exploits the Equation Editor vulnerability (CVE-2017-11882). The document body contains a lure instructing the user to enable content. The presence of RTF_OBJAUTLINK, RTF_EQUATION_EDITOR, and CVE_2017_11882_ACTIVATION_RELATED heuristics strongly indicates exploitation of this known vulnerability. This is a common method for initial access, leading to the execution of a secondary payload.

Heuristics 6

  • Obfuscated Equation Editor ProgID + activation critical CVE related RTF_EQUATION_EDITOR
    RTF decodes to an Equation.3 ProgID from top-level \objdata hex after nested RTF junk groups are ignored, and the document also contains \objemb plus \objupdate activation. This is an obfuscated Equation Editor exploit surface associated with CVE-2017-11882 / CVE-2018-0802 families, but no exact malformed MTEF CVE primitive was recovered from this object.
  • 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.
  • Automatically linked OLE object high RTF_OBJAUTLINK
    RTF contains \objautlink — an automatically linked OLE object surface that can be updated or activated when Word opens the document.
  • \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 1 \objdata section(s) — embedded OLE objects
  • Macro/content-enable lure medium SE_ENABLE_LURE
    Document instructs the user to enable macros or editing — a common technique used by malware droppers to bypass Office macro security settings

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
objdata_00_off00000ef5.bin
a685b00c114db7731b0e36d7c96f963260295876b7cf5bfaba80456c5bfb0b8a		 rtf-objdata-decoded RTF \objdata at offset 0xEF5 1921 bytes

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