So I always thought that you can only SSH into someones iphone if you know his ip address and you are in the same wifi network with your pc. Is it true that you need to be in the same wifi as the iphone to ssh into it? Because then it would be really dangerous to not change the root and mobile passwords!
Various IP scanning techniques can discover devices. Behind firewalls and routers will hide you, but no-one knows if or when a software bug is discovered that a hacker can get thru. Strong passwords are among the best methods to protect yourself.
Absolutely - think router. Millions and millions of routers worldwide. Their job is to transfer data from one network or sub-network (big, small, corporate, home, etc) to another. What data is transferred and what is allowed thru is part of basic router set-up. Usually the defaults are fairly secure. Some WiFi networks (aka: computers behind a router) are more secure than others, that's why computers have firewalls and strong passwords are recommended.
You're welcome. And to be even more safe, have a different password for each log-in. This way if they steal one, the rest are safe. And to be even safer (haha) passwords should contain lower and upper characters, no common words, plus number and special characters (like !?,()$&@;:/-, etc).