The best way to secure your account is, undoubtly the 2FA or the Two Factor Authentication, or as Tibia calls it, Authenticator.
With the authenticator, another person may literally have your account and password and they won't be able to log in.
They'll need ' the second factor ', which is either an object, a tiny eletronic device where you press a button and six digits come up or an application used to generate those number, I personaly use Google Authenticator.
Always have your account registered with your current address and ensure all information on it is accurate and updated.
Make sure you have your recovery key with you, if the authenticator is lost or access to it is lost nobody will be able to access your account, only by using the recovery key will you be able to remove the authenticator.
Go to tibia.com, login your account, manage your account, scroll down to ' Authenticator ' and follow the steps to add an authenticator to your account.
You may choose to either use Authy or Google Authenticator on your mobile device (Android or IOS), I choose Google Authenticator.
Tibia itself has it's own security suggestions, click here for more.
I personally don't use anti-virus, malwares or any other software on my personal computers.
Anti-virus, malwares and such protect your computer in general, the only direct action you can take towards your Tibia account is to have a safe password, (contains more than 8 characters, it contains at least one number, one small case letter, one capital case letter and one special character like an exclamation mark for instance), do not, under any circumstance share you account or let a friend log in just to 'walk around with a fast character', don't log in on shady places like a cyber cafe or a lanhouse and so on and of course, use the authenticator.