Malicious RTF / .DOC — malware analysis report

Static analysis result for SHA-256 a83ad1126712bc96…

MALICIOUS

RTF / .DOC

1.88 MB
MD5: c839f70c7a69a3365529eb4c0ed572a0 SHA-1: b82c482e8467acdcc66022b07c484cc84aa37505 SHA-256: a83ad1126712bc966f7a7664eeaa2dccf4702348ffaaeeefa2e6ba1a5303a45d
220 Risk Score

Malware Insights

MITRE ATT&CK
T1566.001 Spearphishing Attachment T1204.002 Malicious File T1059.003 Windows Command Shell

The RTF document contains multiple indicators of malicious activity, including embedded OLE objects and excessive hex-encoded data. Specifically, the presence of RTF_EQUATION_EDITOR and CVE_2017_11882_RELATED heuristics strongly suggests exploitation of the Equation Editor vulnerability (CVE-2017-11882). The extasciitilde{}1.9MB of hex-encoded data within extasciitilde{}objdata sections likely hides the second-stage payload. The extasciitilde{}objupdate directive further indicates an attempt to automatically activate the embedded OLE object.

Heuristics 5

  • Equation Editor OLE1 native payload — CVE-2017-11882 related critical CVE related CVE_2017_11882_RELATED
    RTF decodes to an OLE1 Equation.3 embedded object whose native data is large and payload-like, and \objupdate requests automatic activation. This is the delivery shape used by Equation Editor RCE documents such as CVE-2017-11882/CVE-2018-0802, but the malformed MTEF record needed for exact 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.
  • \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 ~1965KB 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

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
objdata_00_off00000141.bin
eed9f5eea9e770a9f43f173c8ec91640925dd3f2c0d7238322128c1a682b6642		 rtf-objdata-decoded RTF \objdata at offset 0x141 982841 bytes

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