PHREL 介绍
PHREL 是一个针对每个主机的网络流量限制工具，它会跟踪每个输入流量情况，并通过在 iptables 来配置流量限制。
The inserted chain may either rate limit or block the offending host for a
period of time. The inserted chain is automatically removed when the offending
host’s traffic levels return to normal. PHREL is particularly well suited to
protecting nameservers (DNS) from random hosts that flood requests, and to
preventing SSH brute force login attempts.