Just from personal experience:
My college used to have a rather large lab of SGI INDYs running IRIX 5.X and
they were horribly insecure. They were all hard-routed to the 'net, static
IPs and everything, and were constantly being hacked. We eventually took
them off the main line and put them behind a Linux firewall due to the
nastiness of it all. I highly recommend not leaving IRIX-based machines
sitting out in the cold unless you're VERY good at IRIX.
Tarsi
What I've heard is a very, VERY loose security
profile for the default
install... hack proof IRIX is possible with a good admin, but the
default load is far from secure.
Bill