Malicious RTF — malware analysis report

Static analysis result for SHA-256 5f6451cc9ae30756…

MALICIOUS

RTF

974.2 KB First seen: 2020-07-24
MD5: 3fbaa2b0b4471fec738e10bb859c31ae SHA-1: 8e0a9bbd4780c1d6a19fd285285ff8daa99bab22 SHA-256: 5f6451cc9ae307561d3d775177573fed3015839e6980259a93b6a20f56208e2a
240 Risk Score

Malware Insights

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

The RTF file contains embedded OLE object data, specifically related to Equation Editor. Heuristics indicate the exploitation of CVE-2017-11882, which allows for arbitrary code execution when the embedded object is activated. The ClamAV detection as Rtf.Dropper.Agent-7701975-0 further confirms its malicious nature as a dropper.

Heuristics 6

  • Obfuscated Equation Editor ProgID + activation critical CVE related RTF_EQUATION_EDITOR
    RTF decodes to an Equation.3 ProgID from top-level \objdata hex after nested RTF junk groups are ignored, and the document also contains \objemb plus \objupdate activation. This is an obfuscated Equation Editor exploit surface associated with CVE-2017-11882 / CVE-2018-0802 families, but no exact malformed MTEF CVE primitive was recovered from this object.
  • 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-7631944-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Rtf.Dropper.Agent-7631944-0
  • \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
  • Embedded OLE object medium RTF_OBJEMB
    RTF contains \objemb — embedded OLE object

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
objdata_00_off00000836.bin rtf-objdata-decoded RTF \objdata at offset 0x836 114294 bytes
SHA-256: 38938cb1e2d99b7b94c88f3ad3e454553d4673b1e46775b3fc6df50b0d9dd5a7

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