I suspect the real source of the previous two transmissions is probably a prankster/hacker (instead of an English speaking alien broadcasting 650 million LY from Earth). So, I have installed tcpdump on my network while the Array continues to scan RXJ1242-11. I checked the server logs and wasn't able to find any evidence of an illegal login, but a smart hacker (or a dumb hacker with tools written by smart hackers) can easily cover their tracks. With the packet sniffer in place, I'll have a copy of any new activity on the wire, and if the Array intercepts another signal, I can scan the dump file for suspicious packets on or around the time of the transmission.
I literally have not left my desk for the last 24 hours. It's time to clean up all these dishes and take Buzz for a walk.