This DNS likely participates in DoS attacks. Attackers craft queries with a maximum amplification factor and offer up the victim's IP as the query IP. This results in bandwidth from the attacker getting multiplied by amplification factor and the attackers IP is hidden from the victim.

Rate limiting, blocking abusive IPs, and blocking large transfers like zone transfers can help.

You could be party to a dns amplification attack: https://www.cisa.gov/uscert/ncas/alerts/TA13-088A

& a quote from the article:

>Our findings revealed that we can reduce the overall potential by 80% if we patch around 20% of the most potent amplifiers (see Figure 1).