Filters will prevent new spam referrals from appearing in your account, but they do not work retroactively. As part of the service, I create a new advanced segment called All Users (website-name). It can be used for historical reporting, eliminating the spam traffic and giving you clean metrics.
Getting Your Spam Filter Segment
Segments are associated with login accounts. To get the new Segment, you will be provided with a link by email. Log into Google Analytics, then click the link provided. Select the option Any view. Note: your segment will appear with a different name than shown.
The click the Save button to save the segment in your account.
Using the New Spam Filter Segment
To use it, open your Google Analytics report and click on the All Users box at the top. In the list of Segment Names, you should see that All Users is selected (checked) and a new entry just below it All Users (<your-website-name>).
Uncheck All Users and check All Users (<your-website-name>). Your reports now reflect only real traffic to your website. Note: your segment will appear with a different name than shown.
AdWords Users: note that AdWords data is imported into Google Analytics without a hostname value, so the Valid Hostname filter will cause the segment to drop all AdWords cost and ad information if you apply it. View the AdWords reports with the All Sessions segment.