Win.Dropper.Nanocore-9893680-0 — RTF malware analysis

Static analysis result for SHA-256 09355b70ebee9854…

MALICIOUS

RTF

1.25 MB First seen: 2019-05-31
MD5: cc432bf979fd1b6f81fe7f99008a7bf9 SHA-1: 981d8d8762201250d6bc0f653223973f26ad48da SHA-256: 09355b70ebee98548f31b00460f1e9699c32cca209df3c92b178219d63c7ea2e
464 Risk Score

Malware Insights

Win.Dropper.Nanocore-9893680-0 · confidence 95%

MITRE ATT&CK
T1203 Exploitation for Client Execution

The RTF file contains multiple indicators of exploitation for CVE-2017-8570, including Composite Moniker and Equation Editor CLSID firings. The presence of hex-encoded PE headers within OLE object data strongly suggests the embedding of a malicious executable. ClamAV detections of Win.Dropper.Nanocore-9893680-0 further confirm the malicious nature and likely family of the dropped payload.

Heuristics 11

  • 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.
  • Equation Editor CLSID critical CVE likely RTF_EQUATION_EDITOR
    Equation Editor OLE CLSID found inside an OLE object — exploited by CVE-2017-11882 / CVE-2018-0802 / CVE-2018-0798
  • 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.
  • ClamAV: Win.Dropper.Nanocore-9893680-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Win.Dropper.Nanocore-9893680-0
  • PE header (with DOS stub) in hex data critical RTF_MZ_HEX
    Hex-encoded PE (MZ + DOS stub) found inside RTF — likely an embedded executable payload
  • \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.
  • Large hex data blocks in OLE object high RTF_EXCESSIVE_HEX
    RTF contains ~1290KB of hex-encoded data inside \objdata sections — may hide a payload
  • OLE object data medium RTF_OBJDATA
    RTF contains 7 \objdata section(s) — embedded OLE objects
  • OlePres presentation stream in RTF OLE object medium RTF_OLEPRES_STREAM
    RTF contains an embedded OLE object with an OlePres presentation stream. OlePres is an OLE presentation marker and is not enough on its own to identify CVE-2025-21298.
  • Suspicious extracted artifact info EXTRACTED_FILE_STATIC_TRIAGE
    One or more files extracted from inside this sample matched static suspicious-content checks such as script obfuscation, encoded payload blobs, packed data, or execution/download terms.
  • Embedded URL info EMBEDDED_URL
    One or more URLs were extracted from the document. The URL itself is not a detection — see the per-URL labels for which channel (macro, JS, link annotation, document body, ...) reached each URL.
    URL http://ocsp.thawte.com0 In RTF body
    • http://ts-ocsp.ws.symantec.com07In RTF body
    • http://schemas.openxmlformats.org/drawingml/2006/mainIn RTF body
    • http://crl.thawte.com/ThawteTimestampingCA.crl0In RTF body
    • http://ts-aia.ws.symantec.com/tss-ca-g2.cer0In RTF body
    • http://ts-crl.ws.symantec.com/tss-ca-g2.crl0(In RTF body

Extracted artifacts 7

Files carved from inside the sample during analysis.

FilenameKindSourceSize
objdata_00_off0000002c.bin rtf-objdata-decoded RTF \objdata at offset 0x2C 884 bytes
SHA-256: 08cb831cfd094f7193857584f98ebb419e336c73f0191f78a94fb322b6fcad85
objdata_01_off0002595d.bin rtf-objdata-decoded RTF \objdata at offset 0x2595D 84172 bytes
SHA-256: 0d3775908ff9633231ed31366d571cc52d59ead61d5d35f29339e92b5565ca38
objdata_02_off0004eb28.bin rtf-objdata-decoded RTF \objdata at offset 0x4EB28 484460 bytes
SHA-256: 9f099bcbba5badafb2fb9a42007adbccb39b2599a7267f70c470d0ac1a016d2d
Detection
ClamAV: Win.Dropper.Nanocore-9893680-0
Obfuscation or payload: likely
Carved artifact entropy is 7.59, consistent with packed or encrypted content.
objdata_03_off0013b43e.bin rtf-objdata-decoded RTF \objdata at offset 0x13B43E 382 bytes
SHA-256: 7c829894502990522aaee3764e10dad03b3c7476dec48c4e1d128bb9b9774910
objdata_04_off0013b76e.bin rtf-objdata-decoded RTF \objdata at offset 0x13B76E 789 bytes
SHA-256: 87caf099a20fd4563d975979583365d98bc376a5fd992193cf5da7686fc18198
objdata_05_off0013bdff.bin rtf-objdata-decoded RTF \objdata at offset 0x13BDFF 2633 bytes
SHA-256: 1feb5f150bb35566d1a01fc59a357dc0ea34bc7498e0ec99bd939f6f848044b0
objdata_06_off0013d309.bin rtf-objdata-decoded RTF \objdata at offset 0x13D309 4679 bytes
SHA-256: 0e2ce9d01b0df41beca1d9d003ff4bfe3998a96192a53992dd35145a081e0a27

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