[move-on-by]

Its pretty simple:

> A Domain Name Server (DNS) amplification attack is a popular form of distributed denial of service (DDoS) that relies on the use of publically accessible open DNS servers to overwhelm a victim system with DNS response traffic.

DNS queries are much smaller then DNS responses. Making a huge amount of queries uses less bandwidth then uses to respond - making it a prime candidate for DDOS attacks. Look at your logs, no doubt you will see a large number of requests for various hosts. This is your system being used to attack people. Please close the port.