Ir really depends on the kind of contract you signed when you gained the employment. I wouldn't think it is unreasonable for some sites to block access to time-wasting sites like Facebook etc, but if they're spying on you without you knowing then I would say they're violating some privacy - this will, of course, depend on where you're from. I know if I was being spied on and my boss never informed me they monitor activity, I would take them to an employment court - if they say in the contract that they monitor activity for productivity reasons (and it is within the law), then I wouldn't have a problem with is.