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安装配置脚本（ssh 端口和 ignoreip 自行修改）：

# 安装 fail2ban logd
opkg update
opkg install fail2ban logd

# 创建日志目录
mkdir -p /var/log

# 配置 syslog 写入文件（uci方式）
uci set system.@system[0].log_file='/var/log/messages'
uci set system.@system[0].log_size='10240'  # 10MB
uci commit system
/etc/init.d/log restart

# 创建 dropbear 过滤器
cat > /etc/fail2ban/filter.d/dropbear.conf << 'EOF'
[Definition]
failregex = ^.*dropbear\[\d+\]: Login attempt for nonexistent user from <HOST>:\d+$
            ^.*dropbear\[\d+\]: Bad password attempt for '.*' from <HOST>:\d+$
            ^.*dropbear\[\d+\]: Exit before auth from <<HOST>:\d+>: \(user '.*', .* fails\): Exited normally$
ignoreregex = 
EOF

# 创建 jail 配置
cat > /etc/fail2ban/jail.local << 'EOF'
[DEFAULT]
# 基础封禁参数
bantime = 600
findtime = 600
maxretry = 5

# 递进式封禁设置
bantime.increment = true
bantime.factor = 2
bantime.max = -1

# 惯犯快速通道
recidive.threshold = 3
recidive.bantime = -1

# 网络层配置
banaction = nftables-multiport
chain = input

# 白名单（务必添加你的管理IP！）
ignoreip = 127.0.0.1/8 ::1 192.168.100.0/24 192.168.1.0/24

[dropbear]
enabled = true
port = 22
filter = dropbear
logpath = /var/log/messages
action = nftables-multiport[name=dropbear, port="22", protocol=tcp]
EOF

# 重启 fail2ban
/etc/init.d/fail2ban restart

常用指令：

# 查看 fail2ban 运行状态
/etc/init.d/fail2ban status

# 查看封禁 IP 列表
fail2ban-client status dropbear

# 手动封禁指定 IP
fail2ban-client set dropbear banip 111.183.145.241

# 解封指定 IP
fail2ban-client set dropbear unbanip 111.183.145.241

# 解封所有 IP
fail2ban-client unban --all

# 查看 fail2ban 日志
tail -f /var/log/fail2ban.log

# 重启 fail2ban
/etc/init.d/fail2ban restart

# 查看登录失败日志
cat /var/log/messages | egrep --color=auto "Bad (password|publickey)|invalid user|Connection (closed|refused)|authentication failure|not allowed"

# 测试过滤器规则（建议手动测试一下，前面的正则表达式万一匹配不上那就是白给）
fail2ban-regex /var/log/messages /etc/fail2ban/filter.d/dropbear.conf --print-all-matched

# fail2ban 重读日志，比如删除 nginx 日志后执行，不影响已创建的封禁记录
fail2ban-client flushlogs

常规 Linux 版参考这个：https://www.cnblogs.com/nihaorz/p/19667506