Denis V (Artprima)

Each time you login to your blog WordPress creates a session cookie which is used to authenticate you. 
By default if someone somehow gets your cookies he (or she) is able to use them to compromise your blog 
(even without having to know your password!). To prevent this you may want to make your auth cookies 
ip-dependent so that they could be valid only for that ip which you used during login.
Use this plugin only if you have a static IP or dynamic which doesn’t change too often. Otherwise, you’ll 
have to enter your login and password each time your IP changes.

IP Dependent Cookies

Plugin IP Dependent Cookies makes your Wordpress installation more secure adding your IP to salt (which makes cookies IP-dependent).

jotis

Blue Captcha is a powerful and highly customized WordPress plugin that effectively protects your WP blogs from spammers and unwanted persons. It is easily installed and provides high protection against spammers, bots or unwanted persons.
<h4>Do you like Blue Captcha? Then Support it!</h4>
If you like Blue Captcha, then you can help it grow by <a href="http://mybluestuff.blogspot.gr/p/donate_21.html" rel="nofollow ugc">donating one dollar</a>. Any donation will be highly appreciated and will help in further development of this plugin.
Features:
<ul>
<li>It can be applied to any of the following : login form, registration form, commentary form or password recovery form</li>
<li>It’s highly customized</li>
<li>It has 7 predefined CAPTCHA difficulty levels to choose from – of course, you can adjust your CAPTCHA settings and create a custom level</li>
<li>The possible CAPTCHA customizations are more than enough</li>
<li>It can apply the same or totally different CAPTCHA settings on login form, registration form, commentary form and password recovery form</li>
<li>It can display CAPTCHA to only non-registered users or registered users</li>
<li>It can preview CAPTCHA image before applying it</li>
<li>It supports 5 different fonts and 30 different background images</li>
<li>It supports single or double CAPTCHA layer</li>
<li>It can display up to 20(!) characters on Captcha Images</li>
<li>It is capable of adding extra drawing (lines, circles, grid, transparent lines) on CAPTCHA image</li>
<li>It is capable of keeping log file which registers all activities concerning user logins, user registrations, user comments and password recovery</li>
<li>It has “Hall of Shame” (HoS)</li>
<li>It provides blocking options as well</li>
<li>It can export the entire log file or HoS into CSV file (Excel)</li>
<li>With the help of log file and HoS, it’s easy to track down the IP address of spammers or unwanted persons and ban them for ever</li>
</ul>
You can visit <a href="http://mybluestuff.blogspot.com/p/blue-captcha.html" rel="nofollow ugc">Blue Captcha Page</a> for more information.
<h4>Blue Captcha Translation</h4>
Blue Captcha is now available in Greek, Spanish, Russian, Italian, Brazilian-Portuguese, Serbo-Croatian & Slovenian.
I would be very grateful if someone is willing to translate Blue Captcha to another language. 
For those interested, the template translation file (“blue-captcha.pot”) is located on “languages” folder of blue-captcha plugin.
<h3>Contribution</h3>
Special Thanks To The Following Contributors:
Leon Roskar (http://www.qb.si) => Slovenian Translation 
Borisa Djuraskovic (http://www.webhostinghub.com) => Serbo-Croatian Translation 
João Victor T. Magalhães => Brazilian Portuguese Translation 
Ericka Morales Hernández (http://todoriesgo.net) => Italian Translation 
Alex Balashov => Russian Translation 
Andrew Kurtis (http://www.webhostinghub.com) => Spanish Translation

Blue Captcha

Blue Captcha is a powerful and highly customized WordPress plugin that effectively protects your WP blogs from spammers and unwanted persons.

IP Dependent Cookies vs Blue Captcha