Yep that's what the road sign said.... Really - see for yourself ( Road signs warn of zombies )

Hackers got into a construction road sign and changed the display to show a "custom" message. I bet the sign's manufacturer is wishing they'd used a more secure protocol and mutual authentication mechanism for updating the signs...

Good news is that the .NET Micro Framework V3.0 supports mutual authentication via SSL certificates. So you could build a controller for a sign, such as this with the .NET MF and make it a LOT harder for someone to hack like that.