If no_root_squash is used, remote root users are able to change any file on the shared file system and leave applications infected by Trojans for other users to inadvertently execute

The option 'root_squash' causes files acessed/created by 'root' on the NFS client to be given the permissions of a non-root user on the NFS server. The idea is to increase security by preventing a ownership of the root account on one system 'migrating' to the server."