Malicious Office (OLE) / .XLS — malware analysis report

Static analysis result for SHA-256 286b9d1083c181d6…

MALICIOUS

Office (OLE) / .XLS

159.3 KB Created: 1996-12-17 01:32:42 Authoring application: Microsoft Excel
MD5: 51600265f5c2e8a8b3511b0029bf5a48 SHA-1: be78516cff04ecc253ec74e23bf19f91f8b3c436 SHA-256: 286b9d1083c181d6f98a388a666b02b8956de0d43f432c8cb559b4b4892cd616
280 Risk Score

Malware Insights

MITRE ATT&CK
T1059.001 PowerShell T1218 System Binary Proxy Execution T1071 Application Layer Protocol T1105 Ingress Tool Transfer

The sample is an OLE Excel file with a large slack space anomaly, indicating potential obfuscation or embedded content. Heuristics indicate the use of CreateProcess, ShellExecute, VirtualAlloc, LoadLibrary, and GetProcAddress APIs, suggesting the execution of external code. A critical XOR-encoded string heuristic (key 0xFC) further points to obfuscated malicious content. While no specific document body content directly suggests malicious intent, the combination of API calls and encoding strongly implies the execution of a downloader or dropper. No scripts were extracted, limiting direct analysis of the payload's actions.

Heuristics 7

  • XOR-encoded strings (key 0xFC) critical SC_XOR_ENCODED
    Found 5 Windows library/API name(s) XOR-encoded with single-byte key 0xFC: 'LoadLibraryA', 'GetProcAddress', 'VirtualAlloc', 'CreateProcessA', 'RegOpenKeyExA'
  • Reference to CreateProcess API high SC_STR_CREATEPROCESS
    Reference to CreateProcess API
  • Reference to ShellExecute API high SC_STR_SHELLEXEC
    Reference to ShellExecute API
  • 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 163,080 bytes but its declared streams total only 21,308 bytes — 141,772 bytes (87%) 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).
  • Reference to VirtualAlloc API medium SC_STR_VIRTUALALLOC
    Reference to VirtualAlloc API

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