It's very annoying when you look at the log file, and see people do weird things on your site, look for your install.php file, try to access no permission directories, put bad codes after your domain name, they are trying to hack your site. Every time I check the log file, someone tried it.
Hey, your not the only one. But it's not always hackers sniffing round, I caught 2 Google IP's on my site the other day, I presume they were manual reviewers so I blocked the IP quick. I can tell because they spent 12 minutes on the homepage, 4 minutes on the products page, bought 1 item, left a comment and was about to go onto FAQ but got booted . Oh well, at least google paid me $24
Some might be a white hat looking for holes in your security. I happen to be a white hat in computer and internet security, basically we are classified as the good guys. We wont use an exploit in your site to our advantage, just contact you and let you know the problem and how to fix it.