Windows desktops provide isolation from code running on other
desktops. The most commonly seen desktop switch is from the
default desktop, where user applications run, to the winlogon
desktop. This switch is triggered by pressing Ctrl+Alt+Del to
lock your computer or enter your password. Figure 3-12 shows
CardSpace open in the private desktop.
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Winlogon isolates itself from the default user desktop for the
same reason as CardSpace: to make it more dif?¬?cult for malicious
applications to steal sensitive information. Just like winlogon
protects against software capturing your password,
CardSpace makes it more dif?¬?cult for malicious software to perform
screen-scraping or key-capture attacks.
Features of the CardSpace UI
Figure 3-12 The applications in the background are shown as grayed
out when CardSpace is open. The grayed-out applications are actually
just a bitmap of the default user desktop.
For additional
security, CardSpace
opens on a separate
desktop
Is the Private Desktop Impenetrable?
Impenetrable is a very high bar. Although CardSpace raises the bar and makes
many attacks much more dif?¬?cult, it cannot claim invincibility. The desktop is
vulnerable to hardware-based attacks, where an external keylogger is attached
between the keyboard and the computer so that it can intercept user key
strokes.
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