Malicious RTF — malware analysis report

Static analysis result for SHA-256 1d3b9764a2b2f728…

MALICIOUS

RTF

2.58 MB
MD5: 130985cffff5dba915507dabd4852949 SHA-1: 029433cd3070110bad1dc01142050de54a025101 SHA-256: 1d3b9764a2b2f7286b83e0d3d51e10400efc25a8ad053c811f6e25d84675f35d
400 Risk Score

Malware Insights

MITRE ATT&CK
T1204.002 Malicious File T1566.001 Spearphishing Attachment T1027 Obfuscated Files or Information

The RTF document contains embedded OLE objects and specifically triggers the CVE-2017-11882 vulnerability through the Equation Editor. This indicates a dropper mechanism designed to deliver a secondary payload, as suggested by the presence of PE headers within hex-encoded data and ClamAV detections of packed executables.

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.
  • 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
  • ClamAV detection on extracted artifact critical EXTRACTED_FILE_CLAMAV
    ClamAV flagged at least one file extracted from inside this sample. Even when the wrapping document carries no AV detection of its own, a hit on the carved artifact is a strong indicator the sample is a delivery vehicle.
  • \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 ~1270KB 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_off00000f58.bin
77d251d07d1b84b0516748c455d7b7b14c14c9605334e85903b14a56ad0a5ebd		 rtf-objdata-decoded RTF \objdata at offset 0xF58 635091 bytes
Detection
ClamAV: Win.Packed.Zusy-10043799-0
Obfuscation or payload: unlikely
objdata_01_off00137f57.bin
3fc1cd8454df7586245bba8c2ab8cbda9fb839b38842e97a5b28d5335f762a92		 rtf-objdata-decoded RTF \objdata at offset 0x137F57 386485 bytes

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