NewsForge: PHREL Beats Back DNS Server Attacks

“Running a public name server on the Internet today can be
challenging, when it’s exposed to a neverending flood of attacks
against it. The situation is worse if you’re an ISP that provides
recursive lookups for customers. There are many ways to fight high
traffic levels, such as adding more servers or buying specialized
hardware solutions or firewalls that help to protect against
abusive traffic. Another solution, if you’re running your name
server on a Linux system is PHREL, a Per Host RatE Limiter.

“The problem comes when customer hosts are compromised and used
to send spam, which in turn sends thousands of DNS requests per
minute to your name server as they seek their recipients’ mail
server addresses…”

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