Malicious RTF / .DOC — malware analysis report

Static analysis result for SHA-256 f11fbab5b30a780b…

MALICIOUS

RTF / .DOC

1.77 MB First seen: 2022-03-30
MD5: 78d3393a3451a73912dc68694bfb7e3b SHA-1: c9fbc004fc2c7992222217ddcd9487dc27bf11a7 SHA-256: f11fbab5b30a780b0a0019ad442f9be5317b2bc92a3d1051f48bd2af179692df
220 Risk Score

Malware Insights

MITRE ATT&CK
T1204.002 Malicious File Execution: User Execution: Malicious File T1566.001 Phishing: Spearphishing Attachment

The sample is an RTF document that leverages the Equation Editor vulnerability (CVE-2017-11882) to execute a payload. The presence of OLE object data and specific RTF heuristics strongly indicate this exploit. The decoded OLE object is a native executable, suggesting it's designed to download and run further malicious content. The document body is heavily obfuscated and unreadable, providing no direct clues about the lure.

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 ~1846KB 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_off00001c30.bin
89f7d1fa0e9ef529344a1441a84f48e88c4cd3b677ec0d8617290f835e21ec5e		 rtf-objdata-decoded RTF \objdata at offset 0x1C30 923437 bytes

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