Malicious RTF — malware analysis report

Static analysis result for SHA-256 9b22a6f56f90134e…

MALICIOUS

RTF

1.57 MB First seen: 2022-09-14
MD5: 753aa33a65b8ec3d7c351981029e901c SHA-1: 44930edad569663ae13c65691c931cd1b521dfb7 SHA-256: 9b22a6f56f90134e5c8ac12e813cefa96cb2c9e168ab8af260a93b58a9bc2da1
180 Risk Score

Malware Insights

MITRE ATT&CK
T1566.001 Spearphishing Attachment T1204.002 Malicious File

The RTF file contains an embedded OLE object specifically identified as Equation Editor, triggering heuristics related to CVE-2017-11882. The ".objupdate" directive forces the activation of this embedded object, which is a known method for exploiting this vulnerability. The decoded object data contains what appears to be VBScript code, likely intended to download and execute a second-stage payload.

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_off000012c5.bin
7bb93298e6863ffa58d8f6549cea863a205fc5d5bb3b6a053c16055acd2418c1		 rtf-objdata-decoded RTF \objdata at offset 0x12C5 81013 bytes
objdata_01_off0002ed54.bin
f7b929ce489dfb0e55f3383a35fdd691eace09a148b71bdce40ecf74b197fdc5		 rtf-objdata-decoded RTF \objdata at offset 0x2ED54 346461 bytes

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