Win.Downloader.97183-1 — Office (OLE) / .XLS malware analysis

Static analysis result for SHA-256 6763440e4a186892…

MALICIOUS

Office (OLE) / .XLS

132.5 KB Created: 1996-12-17 01:32:42 Authoring application: Microsoft Excel
MD5: 1d0c8b955eacdb9d3c2a5074eb2d738b SHA-1: dc83040dbf1a015c717f209e53c45b592407d90a SHA-256: 6763440e4a186892e0002a01007678531d988b79a05ed596c78fb4fe90a9568c
622 Risk Score

Malware Insights

Win.Downloader.97183-1 · confidence 95%

MITRE ATT&CK
T1203 Exploitation for Client Execution T1105 Ingress Tool Transfer

The sample is a malicious Microsoft Excel file that exploits CVE-2009-3129 to embed and execute a PE executable. The embedded executable is detected as Win.Downloader.97183-1 by ClamAV. The file also contains suspicious references to Windows APIs like CreateProcess, WriteProcessMemory, and CreateRemoteThread, indicating its downloader functionality. The presence of cmd.exe and embedded URLs suggests it attempts to download and run further malicious payloads.

Heuristics 14

  • CVE-2009-3129 — Excel FEATHEADER record overflow critical CVE exact CVE_2009_3129
    Workbook BIFF stream contains a FEATHEADER (Feature Header) record with anomalous size (record_size=23, isf=2, cbHdrData=4294967295). Legitimate FEATHEADER records are tiny (<100 bytes) and carry cbHdrData values that fit in the record body; the value here is the documented CVE-2009-3129 exploit primitive — cbHdrData drives a memcpy with attacker-controlled size, leading to memory corruption and code execution in Excel 2007/2003.
  • Reference to WriteProcessMemory API critical SC_STR_WRITEPROCESSMEMORY
    Reference to WriteProcessMemory API
  • Reference to CreateRemoteThread API critical SC_STR_CREATEREMOTETHREAD
    Reference to CreateRemoteThread API
  • Embedded PE executable critical OLE_EMBEDDED_EXE
    MZ/PE header found inside document — possible embedded executable
  • ClamAV: Win.Downloader.97183-1 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Win.Downloader.97183-1
  • 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.
  • Reference to CreateProcess API high SC_STR_CREATEPROCESS
    Reference to CreateProcess API
  • Suspicious cmd.exe invocation with execution flag high SC_STR_CMD
    Suspicious cmd.exe invocation with execution flag
  • Reference to LoadLibrary API high SC_STR_LOADLIBRARY
    Reference to LoadLibrary API
  • Reference to GetProcAddress API high SC_STR_GETPROCADDRESS
    Reference to GetProcAddress API
  • OLE document has large unaccounted-for region high OLE_SLACK_ANOMALY
    OLE file is 135,680 bytes but its declared streams total only 24,565 bytes — 111,115 bytes (82%) live in unallocated sector slack. This is the canonical hiding place for pre-macro-era Office exploit payloads (XOR-encoded shellcode reached via a parser pointer-corruption bug in the document structure).
  • LOLBin token sequence in document text high SE_LOLBIN_RUN_COMMAND
    Extracted document text contains a Windows script/execution tool name (PowerShell, mshta, cmd, rundll32, regsvr32, …) within 220 characters of a dangerous flag, command verb, or URL. This is a visible 'run this' instruction in HTML/PDF/RTF lure bodies, or — in macro-laden Office files — the macro's own string-pool entries appearing adjacent in extracted text.
  • Reference to VirtualAlloc API medium SC_STR_VIRTUALALLOC
    Reference to VirtualAlloc API
  • 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://%s:%d/net/B%s/search%s.php
    • http://%s:%d/net/B%s/serinfo
    • http://about:blank

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
embedded_office_0000fbfc.exe
2b41bb117e46c935bf7c205b37449158080c1eca9a9c403c2bc342d97b615fcf		 embedded-pe Office MZ+PE at offset 0xFBFC 71172 bytes
Detection
ClamAV: Win.Downloader.97183-1
Obfuscation or payload: unlikely

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