Linux服务器总是被猜测密码怎么办？这个脚本帮你简单加固

# 查看失败登录记录
lastb
# 结果展示,跟上参数-xx,表示显示多少记录
root     ssh:notty    110.188.85.88    Tue Oct  5 10:46 - 10:46  (00:00)    
pi       ssh:notty    121.180.246.194  Mon Oct  4 10:53 - 10:53  (00:00)    
pi       ssh:notty    121.180.246.194  Mon Oct  4 10:53 - 10:53  (00:00)    
pi       ssh:notty    121.180.246.194  Mon Oct  4 10:53 - 10:53  (00:00)    
pi       ssh:notty    121.180.246.194  Mon Oct  4 10:53 - 10:53  (00:00)    
root     ssh:notty    110.188.84.142   Mon Oct  4 10:09 - 10:09  (00:00)    
root     ssh:notty    110.188.84.142   Mon Oct  4 10:09 - 10:09  (00:00)    
root     ssh:notty    125.70.165.6     Sun Oct  3 09:39 - 09:39  (00:00)    
db2inst1 ssh:notty    152.136.245.102  Sun Oct  3 09:00 - 09:00  (00:00)    
db2inst1 ssh:notty    152.136.245.102  Sun Oct  3 09:00 - 09:00  (00:00)    
db2inst1 ssh:notty    152.136.245.102  Sun Oct  3 08:57 - 08:57  (00:00)    
db2inst1 ssh:notty    152.136.245.102  Sun Oct  3 08:57 - 08:57  (00:00)    
db2inst1 ssh:notty    152.136.245.102  Sun Oct  3 08:55 - 08:55  (00:00)    
db2inst1 ssh:notty    152.136.245.102  Sun Oct  3 08:55 - 08:55  (00:00)    
rx       ssh:notty    152.136.245.102  Sun Oct  3 08:53 - 08:53  (00:00)    
rx       ssh:notty    152.136.245.102  Sun Oct  3 08:53 - 08:53  (00:00)    
rx       ssh:notty    152.136.245.102  Sun Oct  3 08:50 - 08:50  (00:00)    
rx       ssh:notty    152.136.245.102  Sun Oct  3 08:50 - 08:50  (00:00)    
rx       ssh:notty    152.136.245.102  Sun Oct  3 08:48 - 08:48  (00:00)    
rx       ssh:notty    152.136.245.102  Sun Oct  3 08:48 - 08:48  (00:00)

“ Notty”一词仅表示“ no tty”，大致翻译为“ no terminal”。 当您本地登录到任何Linux计算机时，终端将始终在进程列表中显示为“ tty”。 如果通过SFTP建立了连接，或者您正在使用SCP复制文件，那么它将显示为tty（notty）。
Who or what is root@notty?
If you’re looking through WHM’s process manager and you see root@notty mentioned as one of the processes, don’t be alarmed. It’s perfectly normal and it’s definitely not some hacker called ‘Notty’ who has suddenly got root permissions. Be honest, you’re here because you thought that 😉
You may also have seen sshd: root@notty in the output of ps aux too.
Why notty?
The term ‘notty’ just represents ‘no tty’ which roughly translates as meaning ‘no terminal’. When you login locally to any Linux machine the terminal will always appear in the process list as ‘tty’. If a connection is made via SFTP or you are copying files with SCP (as I did here on a test server prior to bringing up the screenshot above) then it will show as no tty (notty).
Where does TTY come from?
Many years ago, user terminals that were connected to computers were clunky and noisy Electro-mechanical Teleprinters also known as Teletypewriters. They took the latter phrase and chopped some characters out to get the TTY abbreviation:
TeleTYpewriter = TTY
Since then, TTY has been used as the shortened name for a text-only console.
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版权声明：本文为CSDN博主「bh6635」的原创文章，遵循CC 4.0 BY-SA版权协议，转载请附上原文出处链接及本声明。
原文链接：https://blog.csdn.net/u013601606/article/details/105226727/

#!/bin/bash
#Denyhosts SHELL SCRIPT
# 分析登录日志文件，筛选失败登录并统计次数存入文件备用
cat /var/log/secure | awk '/Failed/{print $(NF-3)}'|sort|uniq -c|awk '{print $2"=" $1;}' >/root/Denyhosts.txt
# 定义允许失败登录的次数
DEFINE="10"
# 读取文件，并把条件范围内的IP写到hosts.deny中，实现黑名单效果
for i in `cat /root/Denyhosts.txt`
do
  IP=`echo $i|awk -F= '{print $1}'`
  NUM=`echo $i|awk -F= '{print $2}'`
  if [ $NUM -gt $DEFINE ]
  then
    ipExists=`grep $IP /etc/hosts.deny |grep -v grep |wc -l`
    if [ $ipExists -lt 1 ]
    then
      echo "sshd:$IP" >> /etc/hosts.deny
    fi
  fi
done