A business manager sets up Google Analytics but doesn't apply a filter to exclude internal company traffic. After a month of data collection, they correct the setup by adding the filter. What's the status of the data collected during that first month?

The data from the first month will permanently include the internal traffic. Filters in Google Analytics apply to data as it is processed, so they take effect only from the moment they are activated. Historical data that has already been processed is never reprocessed, cleansed or retrospectively filtered. That makes configuration decisions consequential in a way people often underestimate: a missing internal traffic filter permanently inflates a month of sessions and distorts engagement and conversion rates for that period. The practical responses are to set up filters, internal traffic definitions and unwanted referral exclusions before launch, to test them in a development environment first, and where history has been affected, to annotate the period so future analysts know why the numbers look odd, or to use comparisons and segments to exclude the known internal traffic in analysis.