Computational grids are now mainstream facilities for e-research worldwide. While enterprise grids exist within organizations, national grids have become common, usually consisting of government as well as academic facilities. Such facilities are not uncommonly lenient with blanket policies to allow inbound and outbound grid traffic. This is far from ideal, from a security perspective, but given the dynamic nature of grid use, it is impractical to keep restrictive firewalls and manually keep up with on-demand firewall reconfiguration. Other solutions are necessary, where security is not sacrificed.