The important part of ensuring your site / server / vps is being protected is to follow the following guidelines. looking at logs will allow you to determine the attempts made to breakin in or abuse your server, site or host.
Rule 1 : Secure admin areas, point to point access control goes a long way to secure access, use with htaccess and / or firewall.
Rule 2 : Servers dont browse servers, Post attempts - servers dont do POST to other servers block or limit with htaccess or firewall.
Rule 3 : Dsl / Cable / BB / Dynamic IP's, dont accept direct MX from them, this limits the spread of viruses and phishing attempts and spam. Dont accept mail / service from Infected machines
Rule 4 : Block abusive areas of the internet. Dont trust, validate and only institute block on fact not on emotion.