Analytics spam has become a larger and larger issue over the last few years and can cause a lot of headaches and questions when spammers strike a site you are monitoring. Fortunately, there are typically some easy ways to spot spam and fix the issues spam can cause.
If you've noticed a large, unexplained increase in traffic on your site and you don't have a good marketing reason for it, it might be because of spam. The first thing you want to check is if the traffic is all coming from a single traffic source. Most spam comes in the form of 'Direct' traffic. If all or most of your traffic increase is coming from the 'Direct' channel, it's time to investigate further. Most of the time, the spam traffic is going to be coming from a single user/machine or a few users/machines. If all of the new traffic is coming from a single or a select few cities/states or IP addresses, it's extremely likely to be spam traffic.
Fortunately, there is an easy solution to "fix" this problem. All it takes is creation of a new Analytics filter that will filter out the spam traffic, but include the rest of your site's traffic. To do this, you'd want to create a filter in Analytics that removes the spam IP address, their location(s) and perhaps other details if you'd really like to be specific. The important part of this filter is to try and not filter out any or as little of your true web traffic as possible.