Detecting backdoors on Linux x64 systems

BackdoorFinder.java

import java.io.*;
import java.util.*;

public class BackdoorFinder {
    public static void main(String[] args) {
        File file = new File("/etc"); // Good Starting point. Change here if you want another root folder to start from. 
        if (file.exists() && !file.isDirectory()) {
            System.out.println("File is not a directory");
            return;
        }
        findBackdoorFiles(file);
    }

    private static void findBackdoorFiles(File directory) {
        File[] files = directory.listFiles();
        if (files != null) {
            for (File file : files) {
                if (file.isDirectory()) {
                    findBackdoorFiles(file);
                } else {
                    String fileName = file.getName().toLowerCase();
                    if (fileName.endsWith(".sh") || fileName.endsWith(".bash")) {
                        try {
                            BufferedReader reader = new BufferedReader(new FileReader(file));
                            String line;
                            while ((line = reader.readLine()) != null) {
                                if (line.contains("eval") || line.contains("exec")) {
                                    System.out.println("Potential backdoor found: " + file.getAbsolutePath());
                                }
                            }
                            reader.close();
                        } catch (FileNotFoundException e) {
                            e.printStackTrace();
                        } catch (IOException e) {
                            e.printStackTrace();
                        }
                    }
                }
            }
        }
    }
}