Windows Server 2003 comes bundled with a very capable
RADIUS (also known as
AAA) server that's extremely stable, secure, and robust. When you search on Internet security databases for Microsoft IAS vulnerabilities, you won't find any. The IAS service just runs for years without the need to patch IAS. If your Windows Server 2003 box is hardened to only accept IAS requests with host-based firewall restrictions on all other ports and you install no other services on a Windows 2003 box, you can literally keep an IAS RADIUS server up for years of zero downtime or reboots.
http://articles.techrepublic.com.com/5100-10878_11-6148579.html
Microsoft IAS RADIUS for wireless authentication