According to the Austrian regulator, Google Analytics is illegal because the default IP anonymization is not sufficient enough, IT daily says. The DSB concludes that it concerns unique identification numbers and browser parameters. These unique IDs are used to determine whether a website visitor has previously visited a specific website.
Because these are not anonymized enough, you could combine this data into a unique profile and thus trace it back to a natural identifiable person. In addition, the DSB believes that Google does not protect their data enough against the American intelligence services.