Win.Trojan.Koobface-941 — RTF / .DOC malware analysis

Static analysis result for SHA-256 de3c62047fe92666…

MALICIOUS

RTF / .DOC

81.2 KB Authoring application: Msftedit 5.41.15.1515
MD5: aa5552efacd2dbbe07bae6340135955d SHA-1: dc202083b733a23dd9f4ac61d9598d200be7df33 SHA-256: de3c62047fe92666f5be810b31cfd4ab6b1fefdbacca2c1055ab93ab6fd1c320
262 Risk Score

Malware Insights

Win.Trojan.Koobface-941 · confidence 95%

MITRE ATT&CK
T1559.001 Component Object Model T1137.001 DLL Search Order Hijacking

The RTF file contains an embedded OLE object, identified as a package object. Static analysis reveals PE header within the OLE object's data, indicating it is likely an executable. ClamAV signatures confirm the detection of Win.Trojan.Koobface-941, strongly suggesting this is the family. The embedded object is the primary mechanism for delivering the malicious payload.

Heuristics 7

  • 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
  • ClamAV: Win.Trojan.Koobface-941 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Win.Trojan.Koobface-941
  • ClamAV detection on extracted artifact critical EXTRACTED_FILE_CLAMAV
    ClamAV flagged at least one file extracted from inside this sample. Even when the wrapping document carries no AV detection of its own, a hit on the carved artifact is a strong indicator the sample is a delivery vehicle.
  • Package object class high RTF_OBJCLASS_PACKAGE
    OLE Package object — can wrap arbitrary files
  • OLE object data medium RTF_OBJDATA
    RTF contains 1 \objdata section(s) — embedded OLE objects
  • Embedded OLE object medium RTF_OBJEMB
    RTF contains \objemb — embedded OLE object
  • 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.

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
objdata_00_off000000c3.bin
9e6b9ddc5368bc45dbfbadaf34d9f2a774779d613721206ad98b7152fe1ce7a2		 rtf-objdata-decoded RTF \objdata at offset 0xC3 36655 bytes
Detection
ClamAV: Win.Trojan.Koobface-941
Obfuscation or payload: likely
Carved artifact entropy is 7.40, consistent with packed or encrypted content.

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