Judas works by proxying all DNS queries to the legitimate nameservers for a domain. The magic comes with Judas’s rule configurations which allow you to change DNS responses depending on source IP or DNS query type. This allows an attacker to configure a malicious nameserver to do things like selectively re-route inbound email coming from specified source IP ranges (via modified MX records), set extremely long TTLs to keep poisoned records cached, and more.

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