Q: How much more secure does the new User Account Control (UAC) feature in Windows Vista make workstations?
A: UAC makes your workstation OS more secure but doesn't directly make the information stored on the workstation more secure. UAC is intended to prevent malware from leveraging a user’s local administrator authority to compromise the local system. UAC is useful for preventing the reconfiguration of the computer and stopping some types of rootkits, keystroke loggers, and other attacks that typically require administrator authority. However, if a user executes malware, and the intent of the attacker is to simply steal information the user has access to or abuse the user’s access to various applications on the network, UAC can't help because it stops only malware that tries to perform an administrator-level operation, not malware that simply accesses documents and other files the user has access to.
To protect information from theft by malware, you must prevent malware from executing in the first place. Doing so still requires the multipronged approach of traditional safeguards including patching, antivirus software maintenance, and user training.