If someone wants to crack your system really really badly, and they know what they are doing, they may well be able to do so despite your best efforts. On the other hand, if your site is fairly hard to get into that might persuade someone to look for greener pastures.
Protection starts with a password that is difficult to guess.
You want to maximize the password universe that has to be searched by would be crackers. Intersperse upper and lower case letters, numbers and punctuation. Never use a letter string that is a word in any human language. Also stay away from names and phone numbers. Anyone who has a shell account on your system should follow these rules.