linux ssh backdoor,Linux Fokirtor Backdoor [新的Linux后门]

日前，赛门铁克发布博客称，在五月的一次安全事件中，发现一名******了一个大型物联网托管服务商，并且在内部管理系统上使用了一个有意思的Linux后门 – Fokirtor。

经过赛门铁克研究发现，该后门能够伪装它的通信流量，并伪装成正常的SSH通信流量。该后门支持***者运行常用的功能，如执行远程命令、反向链接到C&C服务器，Fokirtor能够监控SSH网络流量，如果检测到流量中存在冒号、感叹号、分号、句号(“:!;.”)，一旦检测到流量存在这些字符，Fokirtor代码能够解析除这些字符之外的流量，然后提取经过Blowfish和Base64加密的命令。

当服务器感染该后门后，它从机器上收集以下信息：1、主机名和IP地址

2、端口

3、密码

4、SSH密钥

5、用户名

收集之后对信息进行加密，并发送到***者的C&C服务器。

赛门铁克分析师表示，要识别网络中是否存在该后门，可以看流量中是否包含了感叹号字符，正常的SSH流量中是不会包含感叹号的。

Linux Fokirtor Backdoor检测脚本#!/bin/sh

#

# A simple check to see if running ssh processes contain any string that have

# been designated an indication of Fokirtor by Symantec.

#

# More info here:

# http://www.symantec.com/connect/blogs/linux-back-door-uses-covert-communication-protocol

#

# (c) 2013, Kumina bv, info@kumina.nl

#

# You are free to use, modify and distribute this check in any way you see

# fit. Just don't say you wrote it.

#

# This check is created for Debian Squeeze/Wheezy, no idea if it'll work in

# other distros. You'll need gdb-minimal (for gcore) installed.

# We need to be root

if [ `/usr/bin/id -u` -ne 0 ]; then

echo "You need root for this script. Sorry."

exit 1

fi

# For all pids of the ssh process, do the check

for pid in `/bin/pidof sshd`; do

t=$(/bin/mktemp)

/usr/bin/gdb

-ex "set pagination off" -ex "set height 0 " -ex "set width 0" \

-ex "attach $pid" -ex "gcore $t" -ex detach -ex quit

i=0

for str in hbt= key= dhost= sp= sk= dip=; do

/usr/bin/strings $t | /bin/grep "${str}[[:digit:]]"

if [ $? -eq 0 ]; then

i=$(($i + 1))

fi

done

/bin/rm $t

if [ $i -eq 6 ]; then

echo "CRITICAL: Fokirtor strings found in sshd process ${pid}!"

exit 2

fi

done

echo "OK: No indication of Fokirtor found."

exit 0