Of course they can tell where you've been surfing. They surely have a firewall which can log all to/from traffic. It's even easier for them if they run a proxy server (which can be run transparently). If you are on the corporate network, the corporation can inspect every network packet entering or leaving your computer.
And as soon as Paladium is released, and tightly integrated wit .NET, Microsoft, Intel, and the government will also have this ability. Resistance is futile. Better to just be a good boy, at least while at work if you value your job.
[ September 12, 2002: Message edited by: void main ]