The camera doesn't broadcast but does listen, by default, to incoming connection on port 80.
As marocoscu mentioned, changing the default port used on the camera is a good first step. Yes, it still allows anyone sniffing traffic in your network from seeing the port, username and password but you might have bigger concerns if you're worried about people sniffing your network traffic.
The other thing I have done is create a user account which does not have admin privileges which I use when connecting via the Internet. This would still allow someone to sniff the traffic but would not allow them to make any config changes on the device. You can also change the password weekly or more often if regularly accessing the camera from outside the LAN.
The other thing you could look at, which I've been meaning to do for a while but haven't gotten to, is tunnelling connections so that traffic to the cameras would be encrypted.