I often receive phishing emails claiming to be big companies like PayPal.
When I check the link I remove anything which could be used to confirm that it was me who clicked and open the link in a virtual machine.
Most of the time the fake sites look to be hosted by small companies. Most likely hacked in some way.
Who should I inform when I think that a site has been compromised?
In the past I have informed the owner and the registrar but never get a response.