1. In DNS, the SOA record is the "root" record for a domain (or "zone"). Hack: If you control the SOA for a reverse mapping, you can spoof the reverse lookup for an IP address. Let's say that you controlled the DNS server for 132.2.0.192.in-addr.arpa, you can choose to return any domain name you want. This can be used to subvert a number of systems that rely upon reverse lookups, such as older /etc/hosts.equiv files (specifically, the older istrusted() function call). From Hacking-Lexicon