Also called "inverse DNS," the PTR record is an option. See reverse DNS. Two Name Server (NS) records identify the authoritative DNS servers for the domain. Required for redundancy, the secondary ...

This relatively short value means that remote DNS resolvers should only cache records retrieved from this ... The first actual record in our sample zone file—or in any normal zone file—is ...

"With this URL, the sample made a request to a DNS server ... and download the Python script payload disguised as TXT records from the DNS server, which would appear as normal requests.