Malicious RTF — malware analysis report

Static analysis result for SHA-256 479ce75e76a0bd5e…

MALICIOUS

RTF

13.1 KB First seen: 2020-07-24
MD5: f460379c2c809e7e01110f67f18180d2 SHA-1: 65f3ca378431690df5c6866ef285553c1b90da9a SHA-256: 479ce75e76a0bd5ed79fb20940332622f5a7eb959dbd4996e4f103132f9a1892
260 Risk Score

Malware Insights

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

The file is an RTF document that contains embedded OLE object data, specifically targeting the CVE-2017-11882 vulnerability in the Equation Editor. This exploit is designed to execute arbitrary code, likely to download and run a secondary payload. The ClamAV signature Rtf.Dropper.Agent-8176610-0 further confirms its malicious nature as a dropper.

Heuristics 6

  • Split hex Equation Editor ProgID + OLE object critical CVE likely 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.
  • 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.
  • ClamAV: Rtf.Dropper.Agent-8176610-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Rtf.Dropper.Agent-8176610-0
  • Automatically linked OLE object high RTF_OBJAUTLINK
    RTF contains \objautlink — an automatically linked OLE object surface that can be updated or activated when Word opens the document.
  • \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 1 \objdata section(s) — embedded OLE objects

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
objdata_00_off000014b0.bin rtf-objdata-decoded RTF \objdata at offset 0x14B0 1533 bytes
SHA-256: 35ac4cff83a5eebe79c47a066233aa38a510c887dca25fc1d2c1993845ce1b70

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