Malicious RTF / .DOC — malware analysis report

Static analysis result for SHA-256 fa7b9d57591d87d9…

MALICIOUS

RTF / .DOC

42.1 KB First seen: 2023-01-30
MD5: 1794db6737e789435439087f483d0700 SHA-1: 3ad8ad2bdb0dd37374b6d9a9700cf7572d9f8151 SHA-256: fa7b9d57591d87d96023f4eef085eb67fdbe92417a29ea10b14ebc4823d67095
200 Risk Score

Malware Insights

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

The sample is an RTF document that leverages the CVE-2017-11882 vulnerability in Microsoft Equation Editor. The document body contains a lure to enable editing, and the heuristics indicate the presence of an OLE object designed to exploit this vulnerability. This exploit is commonly used to download and execute a second-stage payload.

Heuristics 6

  • 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.
  • 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
  • Embedded OLE object medium RTF_OBJEMB
    RTF contains \objemb — embedded OLE object
  • 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_off0000455a.bin
73280ebb6ceb5349069b4bf6aa87f2d008771be8a80bddfacb5e42d724a7aad1		 rtf-objdata-decoded RTF \objdata at offset 0x455A 2145 bytes

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