Malicious RTF — malware analysis report

Static analysis result for SHA-256 644ca0082c5774ea…

MALICIOUS

RTF

1.29 MB First seen: 2021-06-30
MD5: 94908e14b1785a00a96c0f1fbcc019dd SHA-1: 6c0990820e8f5824824d5e815d7a91256682d571 SHA-256: 644ca0082c5774ea88edee9586255b2329ec74e415cb10d91833000d63e693ed
380 Risk Score

Malware Insights

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

The RTF file contains an embedded OLE object that exploits CVE-2017-11882 through the Equation Editor. This exploit is designed to download and execute a secondary payload, as indicated by the presence of RTF_MZ_HEX and RTF_EQUATION_EDITOR heuristics. The ClamAV detection name 'Rtf.Dropper.Agent-9965975-1' further supports its role as a dropper.

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 ~1278KB 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 655366 bytes
SHA-256: cb55a6e38b0b3914933f1812548bcd15e4abf64bb8d012c5dead5786ffc5dec0
objdata_01_off00148e5a.bin rtf-objdata-decoded RTF \objdata at offset 0x148E5A 3546 bytes
SHA-256: 07137f2a82ad68f72265ade0ef8e7a3f452027fecf5fe1091c92f1bc8e074fad

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