Malicious RTF — malware analysis report

Static analysis result for SHA-256 67401dfb76ddb38a…

MALICIOUS

RTF

1.17 MB First seen: 2021-06-13
MD5: 86c43310d0b8c3bc8636da502b6f0b3d SHA-1: fea7393eb6ea36b965c953e438246096e7fce76f SHA-256: 67401dfb76ddb38a32e6692ab78a6d5cf8709f70b343012769891d6c9b5af8bc
180 Risk Score

Malware Insights

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

The RTF file contains multiple indicators of exploitation, specifically ".RTF_EQUATION_EDITOR" and "CVE_2017_11882_ACTIVATION_RELATED" heuristics, pointing to the use of the Equation Editor vulnerability. The presence of embedded OLE objects and the \objupdate directive further suggest that the file is designed to trigger the exploit upon opening, likely leading to the execution of a secondary payload. No specific family could be identified from the available evidence.

Heuristics 5

  • 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 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.
  • \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 2 \objdata section(s) — embedded OLE objects
  • Embedded OLE object medium RTF_OBJEMB
    RTF contains \objemb — embedded OLE object

Extracted artifacts 2

Files carved from inside the sample during analysis.

FilenameKindSourceSize
objdata_00_off00000f5b.bin rtf-objdata-decoded RTF \objdata at offset 0xF5B 52573 bytes
SHA-256: 1e4770cf9832212843c3eaf55e4486fe02f79c08b13123d075b08575bb6944f8
objdata_01_off0002e034.bin rtf-objdata-decoded RTF \objdata at offset 0x2E034 254566 bytes
SHA-256: d58e45cc3a60ce012b53972ea70846c80b4219924e4d59541626e9dbb3083e1d

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