DNS Cache poisoning has affected 500-1000 medium to large size organizations…including American Express and CitiBank.
Windows 2003 and NT4/2000 (with the proper registry key settings) are still vulnerable. By default various UNIX based DNS servers are immune to the attack.
http://isc.sans.org/presentations/dnspoisoning.php
You may want to be a little more alert regarding the sites you visit as they may not be the real thing.
