Protecting against being hacked

Hi,

In my stats log I’ve noticed a lot of entries over the past few days where the page accessed is reported as things like:

src=http%3A%2F%2Fflickr.com.makemyballer.com%2Fload.php
src=http%3A%2F%2Fflickr.com.makemyballer.com%2Fsimple.php

These pages don’t exist on my site and from a quick look I guess they’re obviously some form of bot attempt to hack my site. I have seen similar things like this in my stats before but it seemed to stop after a while. But over the last few days I’m seeing a lot of this kind of thing in my stats logs. The referral domains always seem to be something along the lines of flickr.com.xxxx.com

I’m aware of the timthumb hack and I’ve run checks to make sure I’m not susceptible to that, but I’m not sure what else I need to do to try and make sure my security is up to par.

Can anyone point me in the direction of tips, suggestions or further reading as I’m not sure what I need to be doing to maximise security. Is it possible to block/minimise these kind of attacks via plugins or other means?

I’m obviously no expert on security but I am prepared to try and learn more – I just don’t know where I should start…