2019独角兽企业重金招聘Python工程师标准>>> 
手机杀毒的几种方式：
1. 基于签名的特征码的扫描(hash码-md5特征码的扫描)
特征：只能查杀已知的病毒，不能查杀未知的病毒。
大概原理：根据病毒数据库进行查杀，病毒库中保存病毒对应的hash，通过比较程序签名和病毒库中的签名判断是否病毒。
补充：各杀毒软件的原理都是相同的，区别主要在于杀毒引擎。
杀毒引擎用于获取硬件上文件的hash码，并依据此hash码查询数据库的算法.
2.主动防御
通过监控敏感api进行防御，例如监控以下敏感操作：
更改浏览器主页
注册开机启动的行为
应用程序的内存注入
3.启发式扫描:
根据程序敏感的api 提示风险代码
4.云查杀
利用服务器端的病毒数据库进一步查询可疑程序。
人工智能:引用人工智能算法，即一套复杂的if语句
下面是根据第1种方式实现简单杀毒功能核心程序代码：
package com.alex.mobilesafe.ui;import java.util.List;import android.app.Activity;
import android.content.pm.PackageInfo;
import android.content.pm.PackageManager;
import android.content.pm.Signature;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.graphics.drawable.AnimationDrawable;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.view.MotionEvent;
import android.widget.ImageView;
import android.widget.LinearLayout;
import android.widget.ProgressBar;
import android.widget.ScrollView;
import android.widget.TextView;import com.alex.mobilesafe.util.MD5Encoder;import com.alex.mobilesafe.R;public class AntiVirusActivity extends Activity {protected static final int STOP = 100;private ImageView iv;private ProgressBar pb;private LinearLayout ll;private AnimationDrawable anim;private ScrollView sv;private SQLiteDatabase db;private boolean flagscanning = false;private Handler handler = new Handler() {@Overridepublic void handleMessage(Message msg) {super.handleMessage(msg);if(msg.what==STOP){ll.removeAllViews();anim.stop();}String str = (String) msg.obj;TextView tv = new TextView(getApplicationContext());tv.setText(str);ll.setOrientation(LinearLayout.VERTICAL);ll.addView(tv);sv.scrollBy(0, 20);System.out.println(str);}};@Overridepublic void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.antivirus);//antivirus.db 为手机病毒库db = SQLiteDatabase.openDatabase("/sdcard/antivirus.db", null,SQLiteDatabase.OPEN_READONLY);iv = (ImageView) this.findViewById(R.id.iv);//扫描病毒进度条pb = (ProgressBar) this.findViewById(R.id.progressBar1);ll = (LinearLayout) this.findViewById(R.id.ll);//设置ImageView背景资源为动画文件iv.setBackgroundResource(R.drawable.anti_anim);//sv用来显示病毒的扫描结果sv = (ScrollView) this.findViewById(R.id.sv);anim = (AnimationDrawable) iv.getBackground();}@Overridepublic boolean onTouchEvent(MotionEvent event) {//如果程序正在杀毒过程中，拒绝再次启动杀毒线程if(flagscanning){return false;}//如果用户触摸屏幕，则开启杀毒线程 if (event.getAction() == MotionEvent.ACTION_UP) {flagscanning= true;anim.start();new Thread() {public void run() {// 获取每一个应用程序的签名，签名须与数据库的签名想比较List<PackageInfo> infos = getPackageManager().getInstalledPackages(PackageManager.GET_UNINSTALLED_PACKAGES | PackageManager.GET_SIGNATURES);//设置进度条的扫描范围pb.setMax(infos.size());int total = 0;int virustotal = 0;//设置初始病毒数为0for (PackageInfo info : infos) {total++;try {sleep(20);//只为便于观察扫描效果和进度，无实质作用} catch (InterruptedException e) {e.printStackTrace();}Message msg = Message.obtain();msg.obj = "正在扫描" + info.packageName;handler.sendMessage(msg);Signature[] signs = info.signatures;String str = signs[0].toCharsString();String md5 = MD5Encoder.encode(str);//将应用程序签名与数据库中保存的签名进行比较，如果相一致，则使病毒数加1，并通过handler在界面显示病毒包名Cursor cursor = db.rawQuery("select desc from datable where md5=?",new String[] { md5 });if (cursor.moveToFirst()) {String desc = cursor.getString(0);msg = Message.obtain();msg.obj = info.packageName + ": " + desc;handler.sendMessage(msg);virustotal++;}cursor.close();pb.setProgress(total);}Message msg = Message.obtain();msg.what = STOP;msg.obj = "扫描完毕 ,共发现" + virustotal + "个病毒";handler.sendMessage(msg);flagscanning = false;pb.setProgress(0);};}.start();}return super.onTouchEvent(event);}@Overrideprotected void onDestroy() {if (db.isOpen())db.close();super.onDestroy();}
}
package com.alex.mobilesafe.util;import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;public class MD5Encoder {//获得传入字符串的数据摘要，并通过与操作转化为字符串形式的摘要信息public static String encode(String source){String result = null;try {MessageDigest md = MessageDigest.getInstance("md5");byte[] output = md.digest(source.getBytes());StringBuffer sb = new StringBuffer();for(int i=0;i<output.length;i++){String s = Integer.toHexString(0xff&output[i]);if(s.length()==1){sb.append("0"+s);}else{sb.append(s);}}result= sb.toString();} catch (NoSuchAlgorithmException e) {//since the exception won't never happen , we can process the exception here .//In normal case , we should always throw the exception .e.printStackTrace();}return result;}
}运行效果：
