One problem with Google Analytics is that your account number is viewable to anyone. To see any site’s Google Analytics account all you need to do is simply view source and find the GA code.
It’s so easy to find anyone’s account number that you may find yourself viewing your analytics one day and see some strange behavior. Read this post to see if your Google Analytics account has been hijacked and how to fix it.
How to find out if someone stole your account
To find out if someone stole your Google Analytics account, simply go to Content and then All Pages. If you have pages registering views that are not on your site and never have been, someone else is using your analytics account.
This is what I found one day when I visited Content -> All Pages. Four of these pages are not on my site so I did some digging and found hundreds of pages that were registering views that were never on my site.
The first thing I did and you should too is check to see if your site was hacked. Go to Google and type in site:www.yoursite.com to see if Google has indexed any hacked pages on your site. Check your site and view the source code to see if there is any funny business going on.
If you have verified that your site has not been hacked there is a really simply filter you can apply that ensures that your Google Analytics account tracks ONLY traffic from your site. See the screenshot below.
What is happening here is that you are setting a filter to include only traffic to the hostname that contains something that only your site would have. This will exclude traffic that does not meet this filter.
In my case, I set the filter to include only traffic that contains ericmobley (since my site is ericmobley.net) and this excluded all traffic from the other domains that hijacked my analytics account.