Security - only as good as the weakest link

You might have a very strong and highly protected entrance gate to the castle, but if the castle wall is not good enough, the thief will break in from the wall rather than trying to break in from the gate. This is the mind set of the hackers in the digital world as well where they want to access your systems with the minimum possible effort in order to have the highest gain. The security of your system is only as good as the weakest link in your system. Hackers exploit such weak links to gain access to your systems.