Malicious RTF / .DOC — malware analysis report

Static analysis result for SHA-256 f108a18c3b7eb3ba…

MALICIOUS

RTF / .DOC

43.5 KB First seen: 2023-02-01
MD5: 119ce65d4a9e479cd494c1a6de72c586 SHA-1: 812bc57420005036eca281e3210dc6827709c4e1 SHA-256: f108a18c3b7eb3ba3a30f7535eca4e0a0a1901323052bea2156f67a9cb89788b
220 Risk Score

Malware Insights

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

The file is an RTF document that contains an embedded OLE object. Heuristics indicate that this object exploits CVE-2017-11882, a known vulnerability in Microsoft Equation Editor. The document body contains a lure instructing the user to 'Enable editing', which is a common technique to bypass macro security and activate the embedded exploit. The exploit likely leads to the execution of a secondary payload.

Heuristics 6

  • 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.
  • 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_off00004198.bin
196aa4a2c855a6110f2fa9690e4a8ddf96a8971beb014d42da8aafb414c2a245		 rtf-objdata-decoded RTF \objdata at offset 0x4198 2310 bytes

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