To ensure a high level of security, you should use a router with a hardware
firewall (which should have no rules for port-forwarding configured). Then
double check if you have software that listens on some ports for connections,
like ssh, Apache http server or the MySQL server, stuff like that.
This will make it considerably more difficult to get inside your computer.
To prevent hackers installing new software if they still manage to get into
your machine somehow, you can try making a new password which should:
1. be 7 - 10 signs long for starters
2. include capital letters as well as small ones
3. include numbers
4. include special characters like !, ^, etc.
Also, turn off auto-login if you had it on.
That's all I can think about atm. as far security goes. It's sure a good idea
to wipe the HDD and do a clean install first.
