Malicious RTF — malware analysis report

Static analysis result for SHA-256 4d12eaa093cf1a4a…

MALICIOUS

RTF

42.7 KB First seen: 2021-09-16
MD5: 1994d83d0e5a1cf06198dc47ceb04011 SHA-1: e901c24f95104b9275bcbdb8efd3e0dbcc4eaee0 SHA-256: 4d12eaa093cf1a4a51ecb25a3fe92878cc8e6c531993ddda7311621da586b139
200 Risk Score

Malware Insights

MITRE ATT&CK
T1203 Exploitation for Client Execution T1566.001 Spearphishing Attachment

The RTF file contains multiple indicators of malicious activity, including embedded OLE objects and specific heuristics pointing to the exploitation of CVE-2017-11882 via the Equation Editor. The presence of ".bin" files and the "Script execution terms" heuristic suggest that the exploit is used to download and 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 3 \objdata section(s) — embedded OLE objects
  • Embedded OLE object medium RTF_OBJEMB
    RTF contains \objemb — embedded OLE object
  • Suspicious extracted artifact medium EXTRACTED_FILE_STATIC_TRIAGE
    One or more files extracted from inside this sample matched static suspicious-content checks such as script obfuscation, encoded payload blobs, packed data, or execution/download terms.

Extracted artifacts 3

Files carved from inside the sample during analysis.

FilenameKindSourceSize
objdata_00_off00000020.bin rtf-objdata-decoded RTF \objdata at offset 0x20 20065 bytes
SHA-256: 4e134b55c802ec0951da554d8c1a8a186c9fd8ac2c2fc8ddad6d8e1ad0ad8bb4
Detection
ClamAV: No threats found
Obfuscation or payload: likely
Carved artifact contains 1 shell/COM execution token(s).
objdata_01_off00009d03.bin rtf-objdata-decoded RTF \objdata at offset 0x9D03 1709 bytes
SHA-256: 6ef048de06e9c2e6b420e78a489e52123766b08549a074a5f95b98ffe8558f38
objdata_02_off00009d13.bin rtf-objdata-decoded RTF \objdata at offset 0x9D13 36 bytes
SHA-256: 8935eb605040753f89379b3f05c2cdaefba833ec64299ed9c258020f4c1217b0

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