Malicious RTF — malware analysis report

Static analysis result for SHA-256 8bd78fb70c59756a…

MALICIOUS

RTF

2.86 MB First seen: 2019-05-10
MD5: 31fb1ab9b9ab4143a01111ec52537b05 SHA-1: 74cdc78e755f79c1da82baa9e72885295e754abc SHA-256: 8bd78fb70c59756a48d1f0a5f4ec94a33b0cf148787e2ebb9bdbafef30d9c22d
322 Risk Score

Malware Insights

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

The RTF file contains OLE object data and triggers heuristics related to CVE-2017-8570, indicating it exploits a vulnerability to drop a script. The presence of a PE header within hex data and the ClamAV detection as Rtf.Dropper.Agent-9965975-1 strongly suggest it's a dropper. The embedded URL http://test1.ru/newbuild/t.php?act=hit is likely used to download the secondary payload.

Heuristics 8

  • 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.
  • ClamAV: Rtf.Dropper.Agent-9965975-1 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Rtf.Dropper.Agent-9965975-1
  • 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 ~3001KB of hex-encoded data inside \objdata sections — may hide a payload
  • OLE object data medium RTF_OBJDATA
    RTF contains 6 \objdata section(s) — embedded OLE objects
  • 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://test1.ru/newbuild/t.php?act=hit In RTF body
    • http://schemas.microsoft.com/office/word/2003/wordmlIn RTF body

Extracted artifacts 6

Files carved from inside the sample during analysis.

FilenameKindSourceSize
objdata_00_off00018652.bin rtf-objdata-decoded RTF \objdata at offset 0x18652 885 bytes
SHA-256: 7d5f88680e60b61c3804b4e958745d940ae073cb6f167cc9e0d1a27e8996ab45
objdata_01_off00018d6f.bin rtf-objdata-decoded RTF \objdata at offset 0x18D6F 31944 bytes
SHA-256: 2a8e4bbbfdd32eca563de7df5199c07f3fae0c505e4bbbabecbc4ccace1d2f1c
objdata_02_off00028731.bin rtf-objdata-decoded RTF \objdata at offset 0x28731 482 bytes
SHA-256: 8f35162cb7523f92e9f44d62d12eded23d00d10857cb163693e107bc76bbe0d8
objdata_03_off00028b29.bin rtf-objdata-decoded RTF \objdata at offset 0x28B29 850 bytes
SHA-256: 09101911083786d9efb9e255c375cec31ead142c6eac396391f7d01b420bcc31
objdata_04_off00029234.bin rtf-objdata-decoded RTF \objdata at offset 0x29234 2633 bytes
SHA-256: fe11c27d916ab897eb94064e9631d8a29c847a6db39259bef31578da8d19fdf5
objdata_05_off0002a70e.bin rtf-objdata-decoded RTF \objdata at offset 0x2A70E 1413836 bytes
SHA-256: 25585535d7fbf1f4939f5e847a80e66cbeea053f70dd2e23b936519521bcf9c1

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