Not so... I know how to several ways to bypass these blocks, it's not hard. My employer could not stop me going anywhere, if they tried.
edit: fortunately, for me, I am the person who controls this in my company, and I'm adding rules constantly to curb these practices. But much goes by undetectable...
edit edit: here's a great basic example of one bypass.
but there are others that actually open up the new page inside the current page and the url never changes. there are other services that make a 'tiny' url and never open the full blocked url. other services connect only to the ip address and never search a word in the address bar. To overcome this you could stick on a local 'netnanny' type service, but if the user has access to the machine they can just boot off a live disk and do what they want anyhow... There's no realistic way to stop a determined person who can use google.
Edited by TsVk!, 14 February 2014 - 10:36 PM.