Malicious RTF / .DOC — malware analysis report

Static analysis result for SHA-256 c75afefe9049792d…

MALICIOUS

RTF / .DOC

40.6 KB First seen: 2023-02-20
MD5: 237ca100a1e2d96c21a1933d4d994a0b SHA-1: 0c6d8bf568eb39b759382bfa8e12987d188fbb18 SHA-256: c75afefe9049792dfa51101e6e1a13179a6d38434835f3554b1e1dd63e88ebf1
200 Risk Score

Malware Insights

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

The sample is an RTF document containing an embedded OLE object that exploits the CVE-2017-11882 vulnerability in Microsoft Equation Editor. The presence of RTF_EQUATION_EDITOR and CVE_2017_11882_ACTIVATION_RELATED heuristics confirms this exploit. The document also contains a lure instructing the user to 'Enable editing', a common tactic to bypass security measures and facilitate the execution of the embedded exploit.

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_off00005b5b.bin
7bdbe75bedb9ab1e9d2ce6f8badc29a5b3e0721d50db29465f0ce2b9b6ad211a		 rtf-objdata-decoded RTF \objdata at offset 0x5B5B 1332 bytes

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