The following is not 100% accurate, but represents my understanding of the events currently. I'm trying to get a full description from Christian and will hopefully be able to update this information later today.
Last night around 7:30 pm, Caltech detected evidence of computer virus located behind a linksys router with mac address matching our NAT router, and at the IP 126.96.36.199. We did not initially recognize the mac address as the routers because the labeled mac address was off by a digit, so we were looking for another old router for awhile. In addition, pings to 188.8.131.52 were not working from inside or outside of the martian network, but the router was clearly working.
However, about 5 minutes after Christian and Mike left, I found I could ping the address. When I placed the address into a web browser, the address brought us to the control interface for our NAT router (but only from the martian side, from the outside world it wasn't possible to reach it).
They turned logging on the router (which had been off by default) and started monitoring the traffic for a short time. Some unusual IP addresses showed up, and Mike said something about someone trying to IP spoof warning coming up. Something about a file sharing port showing up was briefly mentioned as well.
The outside IP address was changed to 184.108.40.206 and dhcp which apparently was on, was turned off. The password was changed and is in the usual place we keep router passwords.
Update: Christian said Mike has written up a security report and that he'll talk to him tomorrow and forward the relevant information to me. He notes there is possibly an infected laptop/workstation still at large. This could also be a personal laptop that was accidently connected to the martian network. Since it was found to be set to dhcp, its possible a laptop was connected to the wrong side and the user might not have realized this.