The grid offers significant opportunities for performing wide area distributed computing, allowing multiple organizations to collaborate and build dynamic and flexible virtual organisations. However, existing security firewalls often diminish the level of collaboration that is possible, and current grid middleware often assumes that there are no restrictions on the type of communication that is allowed. Accordingly, a number of collaborations have failed because the member sites have different and conflicting security policies. In this paper we present an architecture that facilitates inter-organization communication using existing grid middleware, without compromising the security policies in place at each of the participating sites. Our solutions are built on a number of standard secure communication protocols such as SSH and SOCKS. We call this architecture Remus, and will demonstrate its effectiveness using the Nimrod/G tools.