Malicious RTF / .DOC — malware analysis report

Static analysis result for SHA-256 fb555a4986b9d888…

MALICIOUS

RTF / .DOC

12.6 KB First seen: 2022-08-02
MD5: 2255c5758734247e71bca4a3c1366133 SHA-1: cc0c947a3bc0821ee53774f3a0b6df5c4ab6568b SHA-256: fb555a4986b9d888f4464d440bb8467ae315c7e12f8502d8604cd5da4f36242d
220 Risk Score

Malware Insights

MITRE ATT&CK
T1566.001 Spearphishing Attachment T1204.002 User Execution: Malicious File T1059.005 PowerShell T1059.001 PowerShell T1059.003 Windows Command Shell

The sample is an RTF document that exploits CVE-2017-11882 through an obfuscated Equation Editor object. The presence of RTF_OBJDATA, RTF_OBJAUTLINK, and RTF_OBJUPDATE heuristics, along with the specific CVE_2017_11882_ACTIVATION_RELATED firing, strongly indicates this exploit. The SE_ENABLE_LURE heuristic suggests the document attempts to trick the user into enabling content, a common delivery mechanism for macro-based malware.

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 2 \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_off00001b95.bin
2b5c24af9613002f4cc6087090215eafcabbdeb8aba1623d304e58f289b46c53		 rtf-objdata-decoded RTF \objdata at offset 0x1B95 1790 bytes

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