The authors of iReboot, a program that sets which OS you want to reboot into, thought they were really clever when they rewrote their program so that Vista users didn't have to go through a UAC (User Access Control) check every time they ran it. Instead what they did was to make they users' systems vulnerable to attack betray their inexperience with Windows programming.

The authors had a classic bad Windows program to begin with, in that it required Administrator access, but their in accurate assumption was that everyone on XP runs as Administrator anyway. On Vista the default is different, and even Administrators have to click a button to continue when executing privileged actions. So they rewrote their program into two halves, one a user mode interface, and the other a Windows service running in a privileged user context such as SYSTEM. The two communicate using standard IPC (interprocess communications).

They view what they did as programming around UAC, but it's not as clever as they think. In fact, the installer for their program required Administrator access and the user has to consent through Administrator access to the installation of a service like this. This means that the user has to trust the program that they install in this case, whether it's a legitimate service or malware.

Now by the same token, what they've done is the right way to write such a program. If you need to perform privileged actions you should separate them into a secure process, but you need to take proper precautions to secure the interface with that process. The facilities for making it secure, such as user impersonation, are rich and well-understood. In fact, the program's authors later describe, in a comment to the same blog entry, how they used .NET to create the IPC mechanism and how it was really easy and powerful,

I read all the time of people becoming inpatient with UAC, but it's there for a good reason. Even if it's not an actual security boundary, it reminds you that something potentially dangerous is happening on the system and you should consider whether you really want to do it. I run it on all my Vista systems; it doesn't happen very often and I don't resent it when it does. If it's happening all the time to you, maybe you need to think about how you're using your computer.

http://blogs.pcmag.com/securitywatch/2008/04/new_windows_utility_claims_to_bypass_uac.php