| Secure Edit ControlsKeePass supports security-enhanced edit controls. |
KeePass was one of the first password managers featuring secure edit controls. The edit controls used in KeePass are resistant to password revealers and password control spies. Additionally, the entered passwords are protected against memory dumping attacks: the passwords aren't even visible in the process memory space of KeePass!
KeePass uses secure edit controls only when the hiding behind asterisks option is turned on! If you show the passwords in plaintext, they won't be protected (secure edit controls are just disabled then, replaced by standard Windows edit controls).
Selection LimitationA limitation of these secure edit controls is that you can't select a range of characters. You for example cannot select 3 characters and replace them by the current contents of the clipboard using the paste command.
If you want to delete all the contents of a secure edit control, press Shift-Home or Shift-End. This will remove all entered characters.
Technical background
If you want to know more about how it's working internally, read this article (by the KeePass author) about secure edit controls:
http://www.codeproject.com/KB/edit/SecEditEx.aspx.