admin-group-minimal: Minimum Administrator Group Membership Check

id: admin-group-minimal

info:
  name: Minimum Administrator Group Membership Check
  author: nukunga[SungHyunJeon]
  severity: medium
  description: |
    Ensure that only essential accounts are members of the Administrators group. Excess or unnecessary accounts can increase the system's vulnerability to compromise.
  impact: |
    Additional accounts in the Administrators group can be leveraged by attackers to gain unauthorized access and execute administrative tasks.
  remediation: |
    Remove unneeded accounts from the Administrators group using:
    > net localgroup administrators [AccountName] /del
  reference:
    - https://isms.kisa.or.kr/main/csap/notice/?boardId=bbs_0000000000000004&mode=view&cntId=85
  tags: account-management,code,windows-audit,kisa,admin-group

self-contained: true

code:
  - pre-condition: |
      IsWindows();
    engine:
      - powershell
      - powershell.exe
    args:
      - -ExecutionPolicy
      - Bypass
    pattern: "*.ps1"
    source: |
      $output = net localgroup administrators | Out-String
      $lines = $output -split "`n"
      $start = $false
      $accounts = @()
      foreach ($line in $lines) {
          # Identify the start of the member list by the separator line
          if ($line -match "^-+") {
              $start = $true
              continue
          }
          # End the member list when reaching the completion message
          if ($start -and $line -match "The command completed successfully") {
              break
          }
          if ($start -and $line.Trim() -ne "") {
              $accounts += $line.Trim()
          }
      }
      # Assume that only one account (the built-in administrator or a renamed equivalent) is necessary.
      if ($accounts.Count -gt 1) {
          "EXTRA_ADMIN_ACCOUNTS_FOUND"
      } else {
          "ADMIN_GROUP_MINIMAL"
      }

    matchers:
      - type: word
        words:
          - "EXTRA_ADMIN_ACCOUNTS_FOUND"
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