storyday

force user login into wordpress only from one browser at the same time 
the last login action will kick out the already logged user 
this is a security plugin for wordpress,install this plugin to avoid simultaneously login

multi-login-checker

force user login into wordpress only from one browser at the same time

David Leonard

Secure your WordPress site with WordPress Secure Login.
WordPress Secure Login provides 2-step verification on login. Once a user submits their login credentials, a One Time Pin (OTP) is emailed to them. They need to enter this OTP in order to continue to login.
Stop Brute force hacking attempts, and keep your data safe!
<pre><code>* Easy to install!
* Easy to replace the Email system with an SMS Gateway
* WordPress 4.0 Ready!
</code></pre>

Secure Login

Secure, 2 step Verification for WordPress login, via One Time Pin (OTP).

multi-login-checker vs Secure Login