Question

In WCF web services (or all web services?), if the client and server times are off you get a security exception.

Can someone explain to me why this is?

It is a pain if you are building client server services and the time has to be accurate?

see: http://msdn.microsoft.com/en-us/library/aa738468.aspx

Answer 1

I strongly suspect that this is to make replay attacks harder. These are attacks where a legitimate request and/or response captured by an attacker is sent again at a later time.