Malicious RTF — malware analysis report

Static analysis result for SHA-256 692785573493c52a…

MALICIOUS

RTF

1.31 MB First seen: 2021-06-30
MD5: 83843fcb0c8179f8816ffeb8c5973dfc SHA-1: e4a60198f4de09c107f9dea6131136e5d1be0863 SHA-256: 692785573493c52a2d44bd6db622db1fd7a9ba866945036de12a6cf08dad8fa4
380 Risk Score

Malware Insights

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

The RTF file contains embedded OLE objects, specifically exploiting the Equation Editor vulnerability (CVE-2017-11882). The presence of RTF_MZ_HEX and RTF_EQUATION_EDITOR heuristics indicates that a PE executable is hidden within the OLE object data. ClamAV detection as Rtf.Dropper.Agent-9965975-1 further confirms its malicious nature as a dropper. The embedded OLE object is likely activated via objupdate, leading to the execution of a second-stage payload.

Heuristics 9

  • Equation Editor CLSID critical CVE likely RTF_EQUATION_EDITOR
    Equation Editor OLE CLSID found inside an OLE object — exploited by CVE-2017-11882 / CVE-2018-0802 / CVE-2018-0798
  • 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.
  • ClamAV: Rtf.Dropper.Agent-9965975-1 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Rtf.Dropper.Agent-9965975-1
  • 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
  • \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 ~1288KB 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_off000011e4.bin rtf-objdata-decoded RTF \objdata at offset 0x11E4 661501 bytes
SHA-256: 308622bef6975dc794d724d3b1304c4b12cc4a2d3dc1dccab1c361316ff2e491
objdata_01_off0014c33e.bin rtf-objdata-decoded RTF \objdata at offset 0x14C33E 3546 bytes
SHA-256: 08b7a8393c8dbc5b535dc75cfb7387bb5aa909feadde2b3b43d0bb13647a0504

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