Windows 7, the latest operating system from Microsoft is also their first operating system that automatically synchronizes the PC clock to an internet source of UTC time (Coordinated Universal Time). From the moment a Windows 7 computer is switched on and is connected to the Internet it will request time signals from the Microsoft time service – time.windows.com.
While for many home users this will save them the hassle of setting and correcting their clock as it drifts, for business users it may be problematic as internet time sources are not secure and receiving a time source through the UDP port on the firewall could lead to security breaches and as Internet time sources can’t be authenticated by NTP (Network Time Protocol) the signals can be hijacked by malicious users.
This internet time source can be deactivated by opening the clock and date dialogue box, and opening the Internet Time tab, clicking the ’Change’ setting button and unchecking the ‘Synchronize with an Internet time server< option.’
Whilst this will unsure no unwanted traffic will be coming through your firewall it will also mean that the Windows 7 machine will not be synchronised to UTC and its timekeeping will be reliant on the motherboard clock, which will eventually drift.
To synchronize a network of Windows 7 machines to an accurate and secure source of UTC then the most practical and simplest solution is to plug in a dedicated NTP time server. These connect directly to a router or switch and enable the safe receiving of an atomic clock time source.
NTP time servers use the highly accurate and secure GPS signal (Global Positioning System) available everywhere on the planet or more localized long wave radio signals transmitted by several national physics laboratories such as NIST and NPL.