Home Operation and Maintenance Linux Operation and Maintenance How to detect and kill Trojans in Linux system

How to detect and kill Trojans in Linux system

Aug 10, 2017 am 11:14 AM
linux system

[导读] 木马和后门的查杀是系统管理员一项长期需要坚持的工作,切不可掉以轻心。以下从几个方面在说明Linux系统环境安排配置防范和木马后门查杀的方法:一、Web Server(以Nginx为例)1、为防止跨站感染,将虚拟主机目

木马和后门的查杀是系统管理员一项长期需要坚持的工作,切不可掉以轻心。以下从几个方面在说明Linux系统环境安排配置防范和木马后门查杀的方法:

一、Web Server(以Nginx为例)

1、为防止跨站感染,将虚拟主机目录隔离(可以直接利用fpm建立多个程序池达到隔离效果)

2、上传目录、include类的库文件目录要禁止代码执行(Nginx正则过滤)

3、path_info漏洞修正:

在nginx配置文件中增加:

if ($request_filename ~* (.*).php) {set $php_url $1;         }if (!-e $php_url.php) {return 404;    }
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4、重新编译Web Server,隐藏Server信息

5、打开相关级别的日志,追踪可疑请求,请求者IP等相关信息。

二.改变目录和文件属性,禁止写入

find -type f -name *.php -exec chmod 444 {} ;find -type d -exec chmod 555 {} ;
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注:当然要排除上传目录、缓存目录等;

同时最好禁止chmod函数,攻击者可通过chmod来修改文件只读属性再修改文件!

三.PHP配置

修改php.ini配置文件,禁用危险函数:

disable_funcions = dl,eval,exec,passthru,system,popen,shell_exec,proc_open,proc_terminate,curl_exec,curl_multi_exec,show_source,touch,escapeshellcmd,escapeshellarg
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四.MySQL数据库账号安全:

禁止mysql用户外部链接,程序不要使用root账号,最好单独建立一个有限权限的账号专门用于Web程序。

五.查杀木马、后门

grep -r –include=*.php  ‘[^a-z]eval($_POST’ . > grep.txtgrep -r –include=*.php  ‘file_put_contents(.*$_POST[.*]);’ . > grep.txt
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把搜索结果写入文件,下载下来慢慢分析,其他特征木马、后门类似。有必要的话可对全站所有文件来一次特征查找,上传图片肯定有也捆绑的,来次大清洗。

查找近2天被修改过的文件:

find -mtime -2 -type f -name *.php
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注意:攻击者可能会通过touch函数来修改文件时间属性来避过这种查找,所以touch必须禁止

六.及时给Linux系统和Web程序打补丁,堵上漏洞

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