一、背景
一大早来公司，登录那台暴露在外网的服务器，登录成功的时候，看到160000+次登录失败的记录，看到这个我和我的小伙伴们都惊呆了，是谁那么执着？小伙伴还开玩笑说是不是谁跟你有世仇啊，这么搞你！来活了，我的服务器我做主，搞起，who怕who？
二、具体操作
1、last看一下是否有异常ip及账户登录记录.
[root@DCGH ~]# last -100
ivandu pts/0 139.130.99.123 Tue Apr 24 20:53 still logged in
ivandu pts/0 139.129.0.194 Tue Apr 24 19:13 - 19:35 (00:21)
ivandu pts/1 139.129.0.194 Tue Apr 24 18:02 - 19:35 (01:33)
ivandu pts/1 139.129.0.194 Tue Apr 24 11:30 - 14:24 (02:53)
ivandu pts/0 139.129.0.194 Tue Apr 24 11:11 - 14:24 (03:13)
reboot system boot 3.10.0-693.17.1. Tue Apr 24 11:10 - 21:45 (10:34)
ivandu pts/2 139.129.0.194 Tue Apr 24 11:04 - 11:04 (00:00)
ivandu pts/1 139.129.0.194 Tue Apr 24 10:26 - 11:10 (00:44)
root pts/0 139.129.0.194 Tue Apr 24 10:19 - down (00:51)
reboot system boot 3.10.0-693.17.1. Tue Apr 24 10:18 - 11:10 (00:51)
.....省略一些
全是熟悉的IP，没有异常！很好！
2.创建新用户，用于切换到root来操作，也可以用命令visudo给该用户配置相关的sudo权限，本例中就直接用此账户su到root了(此处可以参见我之前的加固及sodu相关的文章)。
[root@CLDevOps ~]# useradd -M ivandu
[root@CLDevOps ~]# passwd ivandu
Changing password for user ivandu.
New password:
BAD PASSWORD: The password is shorter than 7 characters
Retype new password:
passwd: all authentication tokens updated successfully.
3.禁止root账户通过ssh来远程登录，编辑/etc/ssh/sshd_config，禁止root用户登录。
[root@CLDevOps ~]# sed -i "/^PermitRootLogin/c\PermitRootLogin no" /etc/ssh/sshd_config
[root@CLDevOps ~]# systemctl restart sshd
4.退出root登录，使用新建用户ivandu来登录。此处为了再次还原当时的处置过程新建的用户ivandu，本人一直有禁止root登录的习惯，希望大家也养成这样的习惯。
Could not chdir to home directory /home/ivandu: No such file or directory
-bash-4.2$ su - root
Password:
Last login: Tue Apr 24 21:47:54 CST 2018 on pts/0
Last failed login: Tue Apr 24 22:12:33 CST 2018 from 42.7.26.88 on ssh:notty
There were 403 failed login attempts since the last successful login.
大家看一下，是不是非常疯狂!一会儿的功夫，又是几百次登录尝试。
5.开始防火墙设置，添加指定网段对ssh所用的端口访问权限。
[root@CLDevOps ~]# firewall-cmd --permanent --add-rich-rule="rule family="ipv4" source address="139.130.99.0/24" port protocol="tcp" port="22" accept"
success
[root@CLDevOps ~]# firewall-cmd --permanent --add-rich-rule="rule family="ipv4" source address="139.129.0.0/24" port protocol="tcp" port="22" accept"
success
6.移除原来firewalld中ssh相关规则，重载firewalld。
[root@CLDevOps ~]# firewall-cmd --permanent --remove-service=ssh
success
[root@CLDevOps ~]# firewall-cmd --reload
success
7.现在可以看一下，指定网段外的ip的22端口是否同，我找了另一台阿里云的机器试了一下，效果如下：
[root@heynick ~]# telnet 106.99.233.115 22
Trying 106.99.233.115...
telnet: connect to address 167.99.233.15: No route to host
8.继续看戏，看一下日志。
[root@CLDevOps ~]# journalctl -ex
Apr 24 22:30:29 CLDevOps sshd[20475]: Failed password for root from 42.7.26.88 port 31228 ssh2
Apr 24 22:30:30 CLDevOps unix_chkpwd[20516]: password check failed for user (root)
Apr 24 22:30:30 CLDevOps sshd[20475]: pam_succeed_if(sshd:auth): requirement "uid >= 1000" not met by user "root"
Apr 24 22:30:31 CLDevOps unix_chkpwd[20517]: password check failed for user (root)
Apr 24 22:30:31 CLDevOps sshd[20479]: pam_unix(sshd:auth): authentication failure; logname= uid=0 euid=0 tty=ssh ruser= rhost=58.218.198.159 user=root
Apr 24 22:30:31 CLDevOps sshd[20479]: pam_succeed_if(sshd:auth): requirement "uid >= 1000" not met by user "root"
Apr 24 22:30:32 CLDevOps sshd[20475]: Failed password for root from 42.7.26.88 port 31228 ssh2
Apr 24 22:30:33 CLDevOps unix_chkpwd[20518]: password check failed for user (root)
Apr 24 22:30:33 CLDevOps sshd[20475]: pam_succeed_if(sshd:auth): requirement "uid >= 1000" not met by user "root"
Apr 24 22:30:33 CLDevOps sshd[20479]: Failed password for root from 58.218.198.159 port 26800 ssh2
Apr 24 22:30:35 CLDevOps sshd[20475]: Failed password for root from 42.7.26.88 port 31228 ssh2
Apr 24 22:30:35 CLDevOps sshd[20475]: error: maximum authentication attempts exceeded for root from 42.7.26.88 port 31228 ssh2 [preauth]
Apr 24 22:30:35 CLDevOps sshd[20475]: Disconnecting: Too many authentication failures [preauth]
Apr 24 22:30:35 CLDevOps sshd[20475]: PAM 5 more authentication failures; logname= uid=0 euid=0 tty=ssh ruser= rhost=42.7.26.88 user=root
Apr 24 22:30:35 CLDevOps sshd[20475]: PAM service(sshd) ignoring max retries; 6 > 3
Apr 24 22:30:38 CLDevOps sshd[20479]: Received disconnect from 58.218.198.159 port 26800:11: [preauth]
Apr 24 22:30:38 CLDevOps sshd[20479]: Disconnected from 58.218.198.159 port 26800 [preauth]
依然还是辣么疯狂！变着ip来搞我呢！早上还换着用户呢!哈哈！
当然我这台机器上的服务监听的其他端口我也是开放着的，那些就没必要怕了，遇到情况另当别论。
9.如果别人只用固定ip来攻击咱，我们单独封锁那个ip就行啦，命令这样的，下面我们来试一下封锁ip：58.218.198.159
[root@CLDevOps ~]# firewall-cmd --permanent --add-rich-rule="rule family="ipv4" source address="58.218.198.159" port protocol="tcp" port="22" drop"
success
[root@CLDevOps ~]# firewall-cmd --reload
success
[root@CLDevOps ~]# firewall-cmd --list-rich-rule
rule family="ipv4" source address="139.130.99.0/24" port port="22" protocol="tcp" accept
rule family="ipv4" source address="139.129.0.0/24" port port="22" protocol="tcp" accept
rule family="ipv4" source address="58.218.198.159" port port="22" protocol="tcp" drop
三、总结
1.要养成良好的习惯，不要干啥只会用root！
2.设置一个复杂度比较高的密码。
3.安全加固很有必要。
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