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Found at: raymii.org:70/Exchange_2010_OWA_lock_users_after_x_amount_of_failed_logins.txt

This is a text-only version of the following page on https://raymii.org:
---
Title       : 	Exchange 2010 - OWA - Lock user after x amount of failed logins
Author      : 	Remy van Elst
Date        : 	19-12-2012
URL         : 	https://raymii.org/s/tutorials/Exchange_2010_OWA_lock_users_after_x_amount_of_failed_logins.html
Format      : 	Markdown/HTML
---
This is a tutorial to set up automatic user lockout in Exchange 2010 - Outlook
Web Acces (OWA). When a user does 5 wrong login attempts, he/she is locked out
from the webinterface. After for example 5 minutes he or she is unlocked again
automatically. This helps you mitigate brute force attacks, since an attacker
can only try 1 password/minute, but the user will not be blocked for to long.
Exchange 2010 has some special register settings to make IIS stop caching,
otherwise it would not work.

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#### Group Policy settings
Execute the following steps on one of your domain controllers.
`Start` -> `Administrative Tools` -> `Group Policy Editor`.
Right click the "Default Domain Policy" (or any other policy where you might
want to apply this).
Click `Edit`
Navigate to: `Computer Configuration` -> `Policies` -> `Windows Settings` ->
`Security Settings` -> `Account Policies` -> `Account Lockout Policy`.
Set the following values: - "Account Lockout Duration": 5 minutes - "Account
Lockout Threshold": 5 invalid logon attempts - "Reset Account Lockout Counter
After": 5 minutes
Adapt this to your own time/threshold if you feel so.
Also make sure the group policy is enforced.
Lets move on to IIS to make sure that OWA does not cache the login token.
### IIS / OWA
Outlook Web Access operates via the IIS server, which when using form based
authentication caches login tokens for a set amount of time. [(See this
link)][2] and [this one][3].
If you have set the above group policy and you test in on the outlook web access
of the exchange server, you will notice that if you have done more than 5 failed
logins you can still login with the good password.
On your IIS server(s) where OWA resides execute the following:
Click `Start`
Click `Run`
Type: `regedit`
Navigate to the following key:
`HKEY_LOCAL_MACHINESystemCurrentControlSetServicesInetInfoParameters`
Click the `Edit` menu, then the `Add` menu, select a `32 bit DWORD` (or just
`DWORD`).
Name it: `UserTokenTTL`
Then set its value to `30`. This means that user tokens will be cached for 30
seconds by IIS.
Now that is also solved.
### Bonus: Active Directory Saved Search to view Locked Out users
Open the `Active Directory Users && Computers` window from the `Administrative
Tools` menu.
Right Click the `Saved Queries`, select `New` -> `Query`.
Name: `Locked Out users` Description: `-`
Click `Define Query`. Click the `Find` dropdown, select `Custom Search`. Select
the `Advanced` tab.
Paste the following LDAP Query:
    
    
    (&&(&&(&&(objectCategory=Person)(objectClass=User)(lockoutTime>=1))))
    
Click `OK`.
Click `OK`.
Now if a users calls you that they cannot login, you can see if they are locked
out via that Saved Search. (Note that you might have to refresh the view a few
times before seeing it.)
   [1]: https://www.digitalocean.com/?refcode=7435ae6b8212
   [2]: http://support.microsoft.com/kb/173658/en-us
   [3]: https://www.microsoft.com/technet/prodtechnol/windowsserver2003/library/iis/6b2e7fcd-5fad-4ac8-ac0a-dcfbe771e9e1.mspx
---
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