Office (OOXML) / .XLSX malware analysis — malicious · 2deb95b1fa7089f3

MALICIOUS

Office (OOXML) / .XLSX

145.0 KB Created: 2020-03-31 21:42:15 UTC Authoring application: Microsoft Excel 15.0300

MD5: da7a65a03ebab043d40ced745f2919e9 SHA-1: a4d9f83d7d4b577fc6ee6cbc80bf36307d0366d2 SHA-256: 2deb95b1fa7089f3cd1137d9d17b1a33566ff31e044d53963f74d61b085c623e

340 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic T1059.003 Windows Command Shell

The file is an Excel macro-enabled spreadsheet containing a Workbook_Open macro. This macro utilizes a character-shift-decoded Shell() call to download and execute a second-stage payload, as indicated by critical heuristic firings. ClamAV detections further confirm its malicious nature as a dropper.

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-7645311-0 critical CLAMAV_DETECTION

ClamAV detected this file as malware: Xls.Dropper.Agent-7645311-0
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` `010e8d05a2d4ad29a35330f4cc0cb0ba955dda2cbdb312f7836d69caca4d25b9`	vba-macro	oletools.olevba.extract_macros (decoded VBA source from OOXML)	2615 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` `3003135b30453683d0167fe863f08379525353dff7aeea7a79dc54fb7c2c08a3`	vba-project	OOXML VBA project: xl/vbaProject.bin	14848 bytes
Detection ClamAV: Xls.Dropper.Agent-7645311-0 Obfuscation or payload: likely Carved macro source contains an auto-exec entry point and execution/download terms.

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