WiFi security is in the news (including here), but remember that an attacker has to be physically close to you to attack you with this new technique. So keep calm and focus on a real security risk where someone can attack you from afar.
Flash is the first major internet video technology. It is also a sewer of security vulnerabilities, and the single biggest attach vector used by the Bad Guys. These days, Flash has been replaced by other more secure technologies, so you really don't want it on your computer.
Here are instructions on how to uninstall Flash. This is without doubt the single most important security step you can take.