The Tierra system is a containment facility for digital organisms. Because Tierra implements a virtual computer, one that has never been implemented in hardware, the digital organisms can only execute on the virtual machine. On any real machine, Tierran organisms are nothing but data. They are no more likely to be functional on a real computer than a program that is executable on a Mac is likely to run on an IBM PC, or that the data in a spread sheet is likely to replicate itself by executing on a machine.
Similarly, the network version of Tierra will create a virtual sub-net, within which the digital organisms will be able to move freely. However, the Tierran digital organisms will not access the real net directly. All communication between nodes will be mediated by the simulation software which does not evolve. When Tierran organisms execute a virtual machine instruction that results in communication across the net, that instruction will be interpreted by the simulation software running on the real machine. The simulation software will pass the appropriate information to a Tierra installation on another machine, through established socket based communication channels. These socket communication channels will only exist between Tierra installations at participating nodes. The digital organisms will not be able to sense the presence of real machines or the real net, nor will they have any way of accessing them.
To further understand the nature of the system, consider a comparison between the Tierra program and the mail program. The mail program is installed at every node on the net and can send data to any other node on the net. The data passing between mail programs is generated by processes that are completely out of control: humans. Humans are beyond control, and sometimes actually malicious, yet the messages that they send through the mail program do not cause problems on the net because they are just data. The same is true of the Tierra program. While the processes that generate the messages passing between Tierra installations are wild digital organisms, the messages are harmless data as they pass through the net. The Tierra program that passes the messages does not evolve, and is as well behaved as the mail program.
A related issue is network load. We do not yet know the level of traffic that would be generated by networked installations of Tierra communicating in the manner described. We will place hard limits on the volume of communication allowed to individual digital organisms in order to prevent mutants from spewing to the net. As we start experimenting with the system, we will monitor the traffic levels to determine if it would have a significant impact on network loads. If the loads are significant, additional measures will need to be taken to limit them. This can be done by charging the organisms for their network access so that they will evolve to minimize their access.
To insure that the experiment is safe, Sun Microsystems has hired an independent security expert, Tsutomu Shimomura (who achieved fame by tracking down and capturing the notorious hacker Kevin Mitnick) to do a security review of the project.