Malicious RTF — malware analysis report

Static analysis result for SHA-256 859a92b3928c1ebd…

MALICIOUS

RTF

35.0 KB First seen: 2023-02-07
MD5: 9ad88e8dbef2a3504695ab12bf86688c SHA-1: 732df4a147ae98f0f4fcfea84af2dcd6224a80d5 SHA-256: 859a92b3928c1ebd7d9eb16fcf622493f4d0ba1c776bf86f62ce9734bde090c8
140 Risk Score

Malware Insights

MITRE ATT&CK
T1566.001 Spearphishing Attachment T1204.002 Malicious File T1059.005 Visual Basic

The RTF file contains an embedded OLE object with a split Equation Editor ProgID, indicating an attempt to exploit the Equation Editor vulnerability (CVE-2017-11882). The ".objupdate" directive forces the OLE object to activate, triggering the exploit. The document body contains a lure instructing the user to 'Enable editing', a common tactic to bypass macro security. The embedded OLE object, when decoded, is likely the exploit payload.

Heuristics 4

  • 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.
  • OLE object data medium RTF_OBJDATA
    RTF contains 1 \objdata section(s) — embedded OLE objects
  • Macro/content-enable lure medium SE_ENABLE_LURE
    Document instructs the user to enable macros or editing — a common technique used by malware droppers to bypass Office macro security settings

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
objdata_00_off0000408b.bin
647feb43671e0ba41357e5d0c6624f18919b5011d0ca04f57d9b30a7d43b60f5
rtf-objdata-decoded RTF \objdata at offset 0x408B 1850 bytes