怎么固定若干PC, 除固定的PC 外，不能 Login, 提高安全性

import java.io.InputStreamReader;
import java.io.LineNumberReader;

class Test {

    public static void main(String[] args) {
        Test test = new Test();
        System.out.println(test.getMACAddress());
    }

    public String getMACAddress() {
        String strMacAddr = null;
        try {
            Process process = Runtime.getRuntime().exec("ipconfig /all");
            InputStreamReader ir = new InputStreamReader(process
                    .getInputStream());
            LineNumberReader input = new LineNumberReader(ir);
            String line;
            while ((line = input.readLine()) != null) {
                if (line.indexOf("Physical Address") > 0) {
                    strMacAddr = line.substring(line.indexOf("-") - 2);
                }
            }
        } catch (java.io.IOException e) {
            System.err.println("IOException " + e.getMessage());
        }
        return strMacAddr;
    }
}