Malicious RTF — malware analysis report

Static analysis result for SHA-256 c849ef328be6a76e…

MALICIOUS

RTF

1.90 MB First seen: 2022-02-16
MD5: 773d38745417406674ec23ef7445f9e6 SHA-1: 7b590795ad032db3eb9df135ef9a4dff1469155d SHA-256: c849ef328be6a76e1643aead6118f0fb2b742a112ca262b713484d421da2a584
220 Risk Score

Malware Insights

MITRE ATT&CK
T1566.001 Spearphishing Attachment T1204.002 Malicious File

The RTF file contains a critical heuristic indicating the exploitation of CVE-2017-11882 via an embedded Equation Editor OLE object. The presence of large amounts of hex-encoded data within the OLE object suggests it is used to hide a malicious payload. The RTF_OBJUPDATE heuristic further indicates that the OLE object is designed to be activated automatically. No scripts were extracted, and no document body was available for analysis, but the exploit itself is sufficient to classify this as a malicious document.

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 ~1991KB of hex-encoded data inside \objdata sections — may hide a payload
  • 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_off0000003d.bin
3d522dd41111dd455941565096be0345b8e0769ed464de7e06bfe608ad0c15f7		 rtf-objdata-decoded RTF \objdata at offset 0x3D 995912 bytes

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