How to prevent multiple user login with same user name and password?
8686
How do I expire a PHP session after 30 minutes?
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Too many password attempts
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Duplicate DB sessions created upon Zend_Auth login
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Pros and Cons for having same form for login, register and forgotten password
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Multiple Passwords on One Account
108819
Why there are many guest accounts on my system?
121891
Solaris let me in with different password with the same 8 first characters
58071
How to safely change username and hostname?
157302
Are user files still private when two sudo users exist in Ubuntu?
94457
Ubuntu 13.04 Login Loop
38665
How to set up Ubuntu for multiple users at the same time?
20946
Use one password for administration and another for system login
90170
How do admins maintain user accounts across hundreds of linux servers?
20941
How to run multiple user X sessions on the same computer, at the same time?
1566
Change password on root user and user account
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Preventing Brute Force Logins on Websites
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Can I Prevent Enumeration of Usernames?