marcucci

This is a very simple plugin that will check to see if a visitor is logged in before allowed your WordPress site to be displayed. 
If they are not it will display the login page of your site. It will also add text on the login page to explain that the site 
required all visitors to login.

Password Protect Plugin for WordPress

Force all visitors to login before accessing your wordpress site and add a message on the login screen explaining that login is required.

Jan Štětina

Forces all users to have a strong password when they’re changing it on their profile page. If user enters a weak password an error message is displayed.
It uses the same algorithm to determine password strength as WordPress.
On multisite, network administrator can define required password strength (Network Admin –> Settings –> Enforce Strong Passwords). On single site it’s admin has this capability (Options –> Enforce Strong Passwords).
Developed for private use, but has perspective for more extensive usage. I can’t guarantee any support in the future nor further development, but it is to be expected. Kindly inform me about bugs, if you find any, or propose new features: <a href="mailto:zaantar@zaantar.eu?subject=[enforce-strong-password]" rel="nofollow ugc">zaantar@zaantar.eu</a>.

Enforce Strong Password

Forces all users to have a strong password when they're changing it on their profile page.

Password Protect Plugin for WordPress vs Enforce Strong Password