Malicious RTF — malware analysis report

Static analysis result for SHA-256 a6a21fdbaab944a9…

MALICIOUS

RTF

2.48 MB First seen: 2022-08-09
MD5: 66816ba7fcfe3124a2ff0cc80d65d13d SHA-1: af5f123b5caec84239106ab913e38514ad0ce429 SHA-256: a6a21fdbaab944a98363b763b550fd42f4b5e1bc87649079ff855ba18137a461
380 Risk Score

Malware Insights

MITRE ATT&CK
T1204.002 Malicious File T1566.001 Spearphishing Attachment

The RTF file contains multiple indicators of exploitation for CVE-2017-11882, including a split Equation Editor ProgID and OLE object data. The presence of a PE header within the hex-encoded OLE object data strongly suggests that a malicious executable payload is embedded. ClamAV detection as Rtf.Dropper.Agent-9965975-1 further confirms its malicious nature as a dropper.

Heuristics 9

  • 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.
  • Composite Moniker in RTF OLE object high CVE related RTF_COMPOSITE_MONIKER_RELATED
    RTF contains Composite Moniker CLSID in OLE object context, but no nearby scriptlet/SCT payload was confirmed. Treat as related moniker attack-surface evidence rather than proof of CVE-2017-8570 exploitation.
  • 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.
  • PE header (with DOS stub) in hex data critical RTF_MZ_HEX
    Hex-encoded PE (MZ + DOS stub) found inside RTF — likely an embedded executable payload
  • ClamAV: Rtf.Dropper.Agent-9965975-1 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Rtf.Dropper.Agent-9965975-1
  • \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 ~1643KB 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
  • Embedded OLE object medium RTF_OBJEMB
    RTF contains \objemb — embedded OLE object

Extracted artifacts 2

Files carved from inside the sample during analysis.

FilenameKindSourceSize
objdata_00_off000012c5.bin
cb834b0d92d2edf987e6356f60e22ccc25edc62190091934bc9d0cba7feedb85		 rtf-objdata-decoded RTF \objdata at offset 0x12C5 827717 bytes
objdata_01_off0019b6f4.bin
ffd8c2482cc64da211bcb7ca32c7331bf3796ad5ca2159f697062f334496c915		 rtf-objdata-decoded RTF \objdata at offset 0x19B6F4 187349 bytes

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