Malicious RTF — malware analysis report

Static analysis result for SHA-256 1b8f31cb1ecd1e90…

MALICIOUS

RTF

340.4 KB First seen: 2021-09-16
MD5: ad421e749a4c5d24e2fd56105a1c18c9 SHA-1: 68e4c9c5c89256b06664a3d1b93f71086408e9ec SHA-256: 1b8f31cb1ecd1e90dd9e61ad47f82a21a82a62579df87c11222f08e18fd3ab54
220 Risk Score

Malware Insights

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

The RTF file contains multiple indicators of OLE object manipulation, specifically related to CVE-2017-8570. This vulnerability is known to be used for dropping and executing script files, such as SCT files, which is a common initial access vector. The presence of composite moniker structures and objdata sections strongly suggests the exploitation of this vulnerability.

Heuristics 6

  • Composite Moniker — CVE-2017-8570 (drops SCT script) critical CVE related CVE_2017_8570
    RTF \objdata decodes to OLE data containing the Composite Moniker — CVE-2017-8570 (drops SCT script) CLSID — the vulnerable control/moniker is embedded directly in the document's object stream, the delivery shape of this exploit. RTF objects auto-render when Word opens the file.
  • Composite Moniker in RTF OLE object high CVE related RTF_COMPOSITE_MONIKER_RELATED
    RTF contains Composite Moniker CLSID in OLE object context, but no nearby scriptlet/SCT payload was confirmed. Treat as related moniker attack-surface evidence rather than proof of CVE-2017-8570 exploitation.
  • Automatically linked OLE object high RTF_OBJAUTLINK
    RTF contains \objautlink — an automatically linked OLE object surface that can be updated or activated when Word opens the document.
  • \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 3 \objdata section(s) — embedded OLE objects
  • Embedded OLE object medium RTF_OBJEMB
    RTF contains \objemb — embedded OLE object

Extracted artifacts 3

Files carved from inside the sample during analysis.

FilenameKindSourceSize
objdata_00_off000007da.bin rtf-objdata-decoded RTF \objdata at offset 0x7DA 75541 bytes
SHA-256: c57f503df3b1a92ca43b7e10f2198c23986f2acebcdd162a6a4e228b35838b3c
objdata_01_off00026e3f.bin rtf-objdata-decoded RTF \objdata at offset 0x26E3F 2632 bytes
SHA-256: 18cff8ef194415d33763880bf64011d23305e4b9143b76244b89e1c53b70a0d5
objdata_02_off000283e2.bin rtf-objdata-decoded RTF \objdata at offset 0x283E2 12297 bytes
SHA-256: 44deae4627fee3c44f54d5bd10477ec2e17f4c08135f08e2417832e36d10d037

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