A trusted hosts list contains a list of “probable” trusted hosts. The host names are gathered from services that are running on a server. This information can be used for subsequent attacks by an attacker.
A trusted host relationship does not necessarily imply a client host is vulnerable, but it does show the client host has established communication with the server. The main purpose of the Trusted Hosts List is that Internet Scanner uses these hosts for spoofing attacks, if the administrator turns on the spoofing attacks. Internet Scanner builds this list from these sources:
Finger output
NFS clients
/etc/exports files
rusers output