Linux-----Ubuntu通过shell脚本将SSH多次登录失败的IP自动加入黑名单

一：与登录相关文件介绍

ubuntu三个文件日志介绍：
1：/var/run/utmp：记录当前正在登录系统的用户信息，默认由who和w记录当前登录用户的信息，uptime记录系统启动时间；

2：/var/log/wtmp：记录当前正在登录和历史登录系统的用户信息，默认由last命令查看；

3：/var/log/btmp：记录失败的登录尝试信息，默认由lastb命令查看。

ubuntu查看失败登录记录，只需要

sudo lastb
#或者
sudo lastb -n 30 #查看最新前30条

二：查看失败登录记录

本人买来的服务器，一直没有用，闲置状态，没有管。虽然改了端口，禁止了root的ssh登录权限。但是只要别人不懒的话，随便用工具扫描端口还是很容易扫描出来的，这不，有人扫描出来啦，还正在用跑字典的形式试图暴力破解登录（好家伙，都已经从a都跑到m了）。

ubuntu@VM-20-6-ubuntu:~$ sudo lastb -n 20
maven    ssh:notty    138.68.86.65     Tue Nov 23 12:58 - 12:58  (00:00)
maven    ssh:notty    138.68.86.65     Tue Nov 23 12:58 - 12:58  (00:00)
maxiao   ssh:notty    138.68.86.65     Tue Nov 23 12:58 - 12:58  (00:00)
maxiao   ssh:notty    138.68.86.65     Tue Nov 23 12:58 - 12:58  (00:00)
maundy   ssh:notty    138.68.86.65     Tue Nov 23 12:58 - 12:58  (00:00)
max      ssh:notty    138.68.86.65     Tue Nov 23 12:57 - 12:57  (00:00)
mawenche ssh:notty    138.68.86.65     Tue Nov 23 12:57 - 12:57  (00:00)
maundy   ssh:notty    138.68.86.65     Tue Nov 23 12:57 - 12:57  (00:00)
max      ssh:notty    138.68.86.65     Tue Nov 23 12:57 - 12:57  (00:00)
max      ssh:notty    138.68.86.65     Tue Nov 23 12:57 - 12:57  (00:00)
mawenche ssh:notty    138.68.86.65     Tue Nov 23 12:57 - 12:57  (00:00)
maverick ssh:notty    138.68.86.65     Tue Nov 23 12:57 - 12:57  (00:00)
mawenche ssh:notty    138.68.86.65     Tue Nov 23 12:57 - 12:57  (00:00)
max      ssh:notty    138.68.86.65     Tue Nov 23 12:57 - 12:57  (00:00)
maverick ssh:notty    138.68.86.65     Tue Nov 23 12:57 - 12:57  (00:00)
mawenche ssh:notty    138.68.86.65     Tue Nov 23 12:57 - 12:57  (00:00)
maverick ssh:notty    138.68.86.65     Tue Nov 23 12:57 - 12:57  (00:00)
maven    ssh:notty    138.68.86.65     Tue Nov 23 12:57 - 12:57  (00:00)
maverick ssh:notty    138.68.86.65     Tue Nov 23 12:57 - 12:57  (00:00)
mauricio ssh:notty    138.68.86.65     Tue Nov 23 12:57 - 12:57  (00:00)

查看失败记录并统计次数，发现最多的已经暴力破解跑了3万多条登录记录，虽然没有成功，但是确实像苍蝇般烦人。所以需要写个脚本将多次尝试登录，并失败的IP加入黑名单。

ubuntu@VM-20-6-ubuntu:~$ sudo lastb |awk '{print $3}'|sort |uniq -c
      1 
      4 119.165.181.251
      4 121.129.214.70
  30573 138.68.86.65
      4 151.50.58.55
      1 151.84.178.182
  30702 159.65.220.140
     54 177.249.47.101
      7 185.245.41.97
  15331 211.246.175.6
      4 24.218.231.49
      4 24.224.178.87
     59 47.102.111.161
      4 82.66.84.2
      4 83.195.190.187
      4 83.228.156.118
    103 83.250.30.182
      4 88.157.49.186
      8 98.40.14.28
      1 Sat
      1 Sun
      1 Wed

三：编写ssh失败登录限制IP脚本

这条命令，可以得到登录失败大于4次的IP，及需要加入黑名单的IP名单。

sudo lastb |awk '{print $3}'|sort |uniq -c|awk '{if ($1 > 4) print $2}'

显示如下：

ubuntu@VM-20-6-ubuntu:~$ sudo lastb |awk '{print $3}'|sort |uniq -c|awk '{if ($1 > 4) print $2}'
138.68.86.65
159.65.220.140
177.249.47.101
185.245.41.97
211.246.175.6
47.102.111.161
83.250.30.182
98.40.14.28

开始写脚本，黑名单文件位置为/etc/hosts.deny，Ubuntu格式为ALL: IP 的方式添加才有效

#!/bin/bash
#set -x
list=$(sudo lastb |awk '{print $3}'|sort |uniq -c|awk '{if ($1 > 4) print $2}')
for ip in ${list}
do
	echo ALL: ${ip} >> /etc/hosts.deny #加入黑名单
	echo > /var/log/btmp	#清空失败记录，防止脚本下次执行重复统计IP
done

四：脚本定时任务

crontab -e
#内容为每1小时执行一次脚本
* */1 * * * sudo bash /home/ubuntu/ssh_deny.sh

完成，服务器也每啥东西，为了测试，我将ssh端口改回默认的22端口，开始钓鱼，等过几个小时，看看/etc/hosts.deny黑名单有没有增加IP。

第二天更新效果：
钓了一晚上的鱼，效果不错

ubuntu@VM-20-6-ubuntu:~$ cat /etc/hosts.deny 
# /etc/hosts.deny: list of hosts that are _not_ allowed to access the system.
#                  See the manual pages hosts_access(5) and hosts_options(5).
#
# Example:    ALL: some.host.name, .some.domain
#             ALL EXCEPT in.fingerd: other.host.name, .other.domain
#
# If you're going to protect the portmapper use the name "rpcbind" for the
# daemon name. See rpcbind(8) and rpc.mountd(8) for further information.
#
# The PARANOID wildcard matches any host whose name does not match its
# address.
#
# You may wish to enable this to ensure any programs that don't
# validate looked up hostnames still leave understandable logs. In past
# versions of Debian this has been the default.
# ALL: PARANOID

ALL: 138.68.86.65
ALL: 159.65.220.140
ALL: 177.249.47.101
ALL: 185.245.41.97
ALL: 211.246.175.6
ALL: 47.102.111.161
ALL: 83.250.30.182
ALL: 98.40.14.28
ALL: 220.129.62.150
ALL: 24.245.227.211
ubuntu@VM-20-6-ubuntu:~$ 

失败登录记录也只有几条而已了

ubuntu@VM-20-6-ubuntu:~$ sudo lastb 
pi       ssh:notty    122.199.7.19     Wed Nov 24 05:39 - 05:39  (00:00)
pi       ssh:notty    122.199.7.19     Wed Nov 24 05:39 - 05:39  (00:00)
pi       ssh:notty    122.199.7.19     Wed Nov 24 05:39 - 05:39  (00:00)
pi       ssh:notty    122.199.7.19     Wed Nov 24 05:39 - 05:39  (00:00)

btmp begins Thu Jul 26 22:17:36 1917
ubuntu@VM-20-6-ubuntu:~$