The first thing hackers see before trying to apply any cracking attempts on your wordpress-based websites is the version of wordpress you are having. Experts say you should hide that version number from your output html to make it difficult for crackers to get into your site.
Prior to wordpress 2.5, this was written in header.php theme file. So you could simply delete that line:
<meta name=”generator” content=”WordPress <?php bloginfo(‘version’); ?>” />
But from wordpress 2.5 onward, this is generated automatically by wordpress core engine and inserted in <head> part of your site’s HTML. I have written a little plugin “hide-wp-generator” that hides meta-generator tag altogether and thus helps you keeping your site secure.