Office (OOXML) / .XLSX malware analysis — malicious · bc1ba8502908f7f1

MALICIOUS

Office (OOXML) / .XLSX

13.0 KB Created: 2020-04-07 09:55:46 UTC Authoring application: Microsoft Excel 15.0300

MD5: 0db2c68f375d281b74ed8933c5a87ecb SHA-1: a6f38f670d95f51283707ac5e1e259cac84b86d6 SHA-256: bc1ba8502908f7f16b632d64b9078372f97671d28daacd91c2a43334c5c72485

340 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic T1059.003 Windows Command Shell

The file is an Excel macro-enabled document containing a Workbook_Open macro. This macro utilizes character-shifting functions (Asc, Chr, Mid) to decode and execute a command via Shell(). ClamAV signatures indicate this is a known dropper, likely responsible for downloading and executing a second-stage payload.

Heuristics 7

Shell() call in VBA critical OLE_VBA_SHELL

Shell() call in VBA
VBA character-shift decoded Shell command critical OLE_VBA_ASC_CHR_SHIFT_SHELL

VBA auto-exec macro stores an encoded command string, decodes it with a Mid/Asc/Chr character-shift loop, and passes the recovered text to Shell. This is a high-confidence command stager.
ClamAV: Xls.Dropper.Agent-7652927-0 critical CLAMAV_DETECTION

ClamAV detected this file as malware: Xls.Dropper.Agent-7652927-0
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.
Workbook_Open macro high OLE_VBA_WBOPEN

Workbook_Open macro
Suspicious extracted artifact high 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.
VBA project inside OOXML medium OOXML_VBA

Document contains vbaProject.bin — VBA macros present

Extracted artifacts 2

Files carved from inside the sample during analysis.

Filename	Kind	Source	Size
`macros.bas` `38b09cc4cee857956da7552b7ac76cad39297ea2437d52ed0499d1ba7d619547`	vba-macro	oletools.olevba.extract_macros (decoded VBA source from OOXML)	3097 bytes
Detection ClamAV: No threats found Obfuscation or payload: likely Carved macro source contains an auto-exec entry point and execution/download terms.
`vbaProject_00.bin` `e08e2284379c2aa901854bc02745310aa02d567eea99ab36735457a81cfde986`	vba-project	OOXML VBA project: xl/vbaProject.bin	15360 bytes
Detection ClamAV: Xls.Dropper.Agent-7652927-0 Obfuscation or payload: likely Carved macro source contains an auto-exec entry point and execution/download terms.

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