Malicious RTF — malware analysis report

Static analysis result for SHA-256 4dac63c4108d147f…

MALICIOUS

RTF

1.64 MB First seen: 2021-06-30
MD5: 77ce408ace2b22fa6ebd487cf7c0b949 SHA-1: 82c3b0df35e96c5f7a69ce8a4eb971c96fa9bdd0 SHA-256: 4dac63c4108d147f3525432fcbc145de5d3c8b0faf5d30fe252f1661664e5b63
240 Risk Score

Malware Insights

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

The RTF document contains multiple indicators of malicious activity, including embedded OLE objects and specific heuristics pointing to the CVE-2017-11882 vulnerability. The presence of a large, hex-encoded OLE object suggests it is used to hide a secondary payload, likely executed through the exploitation of this known Microsoft Office Equation Editor vulnerability. The primary attack vector is inferred to be spearphishing attachment.

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 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.
  • \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 ~1716KB 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 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
objdata_00_off000000bb.bin rtf-objdata-decoded RTF \objdata at offset 0xBB 858497 bytes
SHA-256: a8be632fdbf36921004b735ee08d9b050ebf0419a66dae8f7e4ab1136cfccf7d

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