Charles got a new Eero mesh router all set up (Eero is a sponsor of the TWiT Network), but now he gets a warning that his router can be seen online. Leo says that the best thing a router can do is be invisible by not responding to any online queries. It's called Stealth Mode. That's what GRC's Shields Up will test. Most routers have PING turn on by default. But you can turn it off in the security settings. Also, turn off universal plug n play and file sharing.
Richard ran Shields Up! recently, and it all came back as "stealth." Then he installed iTunes and now three results come back as "closed." Leo says that "closed" is OK. He won't want the results to come back as open. This is why Shields Up! was invented, because software like iTunes ends up making computers visible. Leo also recommends turning off Universal Plug and Play (UPnP).
Francine has been running Shields Up! from GRC and it keeps failing. She used to be "stealth" but lately she isn't. Leo says it's a router issue. Router makers decided to make routers easy to set up, but they ended up leaving everyone vulnerable, especially with instant UPnP connection. In fact, there's a new UPnP test on grc.com that Leo recommends everyone run to see if their routers are vulnerable.