Malicious RTF / .DOC — malware analysis report

Static analysis result for SHA-256 1a92c51a7e906d70…

MALICIOUS

RTF / .DOC

21.3 KB First seen: 2022-10-12
MD5: 8c1627e509cfa3f9652b1a0f54342350 SHA-1: c8b7dea996edda5b58e586368e54a7b239bcaf2b SHA-256: 1a92c51a7e906d703ce0cee5f25f0ed22d6ae6588b389635cf1a10d996fc19aa
200 Risk Score

Malware Insights

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

The sample is an RTF document containing an embedded OLE object that exploits CVE-2017-11882 via the Equation Editor. The document body contains a lure instructing the user to 'Enable editing', a common tactic to bypass macro security. The exploitation of Equation Editor and the user enablement lure strongly suggest the document is designed to execute 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.
  • \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
  • Embedded OLE object medium RTF_OBJEMB
    RTF contains \objemb — embedded OLE object
  • 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_off00001b23.bin
9c7ec3c181eeaae5b41580b1b8886572f2e7000e7ce5307f37babf07cc78369f		 rtf-objdata-decoded RTF \objdata at offset 0x1B23 1534 bytes

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