Sometimes the screen will get black and it will say "Movies - Front Row ... " and some other options. Then it will get normal again.
Pair your remote or disable IR receiver (if you do not have a remote) as it may be another person's remote that is launching FrontRow. This can be done in System Preferences -> Security -> General.
I use an unsecured network in the building. This is also worrying me. Can other people see what I am doing?
Using an unsecured network is risky. Specifically, other users can capture all traffic that is not encrypted (SSL). They cannot see what you are doing that only occurs within your system but they have access to all traffic that travels through the network (between your computer and the router) that is not encrypted.
This means that all of your browsing activity can be observed and your emails can be read if your email provider does not use full session encryption. Gmail uses
full session encryption but I do not think that hotmail does yet. Bank websites usually have full session encryption.
Software, such as Ettercap, allows them to tag along with you from site to site by showing the web pages you visit in their web browser. A packet sniffer will capture your IM chats and emails in plain text if those services are not encrypted.
Nothing has to be installed on your system for a MITM attack to work. It is all done on the attackers system. Your system gets tricked into thinking that the attackers computer is the router and then after the attacker's computer logs the traffic it sends the traffic to the router.
There are even methods to trick other users into thinking that they are using encryption when they are not. All of this can be done without your authorization and without you even knowing about it unless you know specifically how to detect such activities.
All of these attacks are very easy to do. They all can be done using GUI based software. No operating systems have built in defences to these kinds of ARP poisoning attacks.
I would never use an unsecured network because you have no idea who else is connected to it. I would connect to a secured network that I do not administrate if I know the network administrator and felt they made good decisions about who they allow connect to the network.
If I do connect to large public networks, such as a coffee shop or university, I run a program called
Mocha because it will give me an alert in the lower left corner of my display when someone is attempting to poison the ARP table to perform MITM attacks.
Could they have access or have installed a virus in my computer?
They would need your admin password to install a virus. Perian is safe; you do not need to worry about installing it. It is a codec pack that lets you use a lot more media formats.
