晚上收到腾讯云短信提示中木马了：
赶紧登录服务器调查，起初怀疑网站有漏洞，调查后发现我设置的 FTP 用户名密码太简单了，被人暴力破解了：
# grep failed /var/log/messages | wc -l
1008
# grep failed /var/log/messages | tail -10
Jan 16 22:57:06 VM-4-3-centos pure-ftpd: ([email protected]) [WARNING] Authentication failed for user [www-data]
Jan 16 22:57:11 VM-4-3-centos pure-ftpd: ([email protected]) [WARNING] Authentication failed for user [www-data]
Jan 16 22:57:15 VM-4-3-centos pure-ftpd: ([email protected]) [WARNING] Authentication failed for user [www-data]
Jan 16 22:57:21 VM-4-3-centos pure-ftpd: ([email protected]) [WARNING] Authentication failed for user [www-data]
Jan 16 22:57:26 VM-4-3-centos pure-ftpd: ([email protected]) [WARNING] Authentication failed for user [www-data]
Jan 16 22:57:30 VM-4-3-centos pure-ftpd: ([email protected]) [WARNING] Authentication failed for user [www-data]
Jan 16 22:57:34 VM-4-3-centos pure-ftpd: ([email protected]) [WARNING] Authentication failed for user [www-data]
Jan 16 22:57:37 VM-4-3-centos pure-ftpd: ([email protected]) [WARNING] Authentication failed for user [www-data]
Jan 16 22:57:43 VM-4-3-centos pure-ftpd: ([email protected]) [WARNING] Authentication failed for user [www-data]
我已经修改了 FTP 登录信息，改用更加复杂的密码了，并重启了 FTP 服务。现在还想想了解下如何防止暴力破解？
环境：腾讯云轻量服务器官方宝塔控制面板（CentOS）+ Pure-FTPd