A name server (NS) record stores the DNS servers authorized by a domain.

The problem with NS servers is that they usually have multiple NS records because of load balancing; for example: hola.fulanito.com points to ns.mimamamemima.com and ns.chompiras.com.

Here, the load is divided in two; therefore, if one of these servers is owned by a malicious user, we will be pointed to a malicious site approximately 50% of the time.