最近学习到linux系统日志和计划任务,下班回家的地铁上有了灵感,尝试编写了自己的第一个脚本,监测如果有恶意登录服务器的话,发邮件通知管理员。暂时还没学习到如何发邮件给管理员,目前只是命令行的提醒和日志记录;脚本的内容也比较简单,都是学习过的基本知识,活学活用。
1、首先编写一个脚本:
定义一个变量LT,变量的值为lastb命令列出的行数(即无效登录的次数,如有恶意登录的话行数会变多);
执行一个if判断语句,如果定义的值大于15次的话,判断为恶意登录,通知管理员。
脚本内容如下:
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[root@localhost ~]
# cat lt.sh
#! /bin/bash
#定义变量LT,记录无效登录的次数;
LT=`lastb |
wc
-l |
cut
-d
' '
-f 1`
if
[ $LT -gt
"15"
]
#判断无效登录的次数如果大于15的话,执行下面的操作;
then
echo
"somebody try to login please check log"
#打印有人尝试登录系统请检查日志
fi
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2、编写一个计划任务
每隔一分钟自动执行上面的脚本
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[root@localhost ~]
# crontab -l
*
/1
* * * *
/bin/sh
/root/lt
.sh
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3、查看效果
超过15次登录在当前命令行模式会提示,有一封新邮件在/var/spool/mail/root下;
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[root@localhost ~]
#
You have new mail
in
/var/spool/mail/root
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查看新邮件,会发现脚本里面的内容,证明有人在尝试登录主机;
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[root@localhost ~]
# tail -2 /var/spool/mail/root
somebody try to login please check log
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执行lastb命令查看发现很多登录失败的记录
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[root@localhost ~]
# lastb |head
user1
ssh
:notty 192.168.22.1 Tue Apr 21 22:04 - 22:04 (00:00)
user1
ssh
:notty 192.168.22.1 Tue Apr 21 22:04 - 22:04 (00:00)
user1
ssh
:notty 192.168.22.1 Tue Apr 21 22:03 - 22:03 (00:00)
user1
ssh
:notty 192.168.22.1 Tue Apr 21 22:03 - 22:03 (00:00)
user1
ssh
:notty 192.168.22.1 Tue Apr 21 22:03 - 22:03 (00:00)
user1
ssh
:notty 192.168.22.1 Tue Apr 21 22:03 - 22:03 (00:00)
user1
ssh
:notty 192.168.22.1 Tue Apr 21 22:03 - 22:03 (00:00)
user1
ssh
:notty 192.168.22.1 Tue Apr 21 21:29 - 21:29 (00:00)
user1
ssh
:notty 192.168.22.1 Tue Apr 21 21:29 - 21:29 (00:00)
user1
ssh
:notty 192.168.22.1 Tue Apr 21 21:29 - 21:29 (00:00)
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查看/var/log/secure 日志也会发现有多次登录失败的记录
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Apr 21 22:03:35 localhost unix_chkpwd[1501]: password check failed
for
user (user1)
Apr 21 22:03:35 localhost sshd[1499]: pam_unix(sshd:auth): authentication failure;
logname
= uid=0 euid=0
tty
=
ssh
ruser= rhost=192.168.22.1 user=user1
Apr 21 22:03:36 localhost sshd[1499]: Failed password
for
user1 from 192.168.22.1 port 50591 ssh2
Apr 21 22:03:39 localhost unix_chkpwd[1502]: password check failed
for
user (user1)
Apr 21 22:03:41 localhost sshd[1499]: Failed password
for
user1 from 192.168.22.1 port 50591 ssh2
Apr 21 22:03:44 localhost unix_chkpwd[1503]: password check failed
for
user (user1)
Apr 21 22:03:46 localhost sshd[1499]: Failed password
for
user1 from 192.168.22.1 port 50591 ssh2
Apr 21 22:03:49 localhost unix_chkpwd[1504]: password check failed
for
user (user1)
Apr 21 22:03:51 localhost sshd[1499]: Failed password
for
user1 from 192.168.22.1 port 50591 ssh2
Apr 21 22:03:52 localhost sshd[1499]: Failed password
for
user1 from 192.168.22.1 port 50591 ssh2
Apr 21 22:03:54 localhost sshd[1500]: Received disconnect from 192.168.22.1: 0:
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根据访问日志的来源IP,我们可以对来源设置iptables规则,禁止访问服务器的22端口,或者封闭ip地址;
暂时只有这么多,小小的骄傲一下,给自己增加点自信心,相信之后的学习中会更加深入了解linux;
和大家分享一下,共勉之。
本文转自 模范生 51CTO博客,原文链接:http://blog.51cto.com/mofansheng/1636847,如需转载请自行联系原作者