Malicious RTF — malware analysis report

Static analysis result for SHA-256 bbf786a31faf279a…

MALICIOUS

RTF

1.48 MB First seen: 2021-06-04
MD5: 0fd080599f043cddd074a38b34a94bdb SHA-1: fbe2e0cdc2ce89fa4f1b2bdd33161d357dbab7a3 SHA-256: bbf786a31faf279a95de40449f85ad0532478e21d3bc4be88bbf65c7370e7fae
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 related to CVE-2017-11882 via the Equation Editor. The presence of OLE objects and the ".objupdate" directive strongly suggest that the file is designed to trigger this vulnerability upon opening. This exploit is commonly used to deliver secondary payloads, hence the high confidence in an attack pattern involving code execution and potential payload download.

Heuristics 5

  • 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 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_off00000f58.bin rtf-objdata-decoded RTF \objdata at offset 0xF58 35432 bytes
SHA-256: 82fbc8858551e32b022a612b2070a4208c395e88761b7e36fe60d0a4cd784981
objdata_01_off0001f37e.bin rtf-objdata-decoded RTF \objdata at offset 0x1F37E 386485 bytes
SHA-256: 02caa540b4e047d624c4392bc52a3662b57dab578bd1a3358b99362f97cf411d

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