One of the biggest annoyances among marketers and web analytics folks at all levels is referrer spam. Often, upward of 600 sessions a week aren't even sessions, but are "ghost" sessions from referrers that want you to visit their sites after seeing them in your referral reports.
If you have a large user base, 600 additional sessions might not even register. But for smaller sites, it's a real pollution problem. There are lots of fixes and solutions (our favourite so far as been Referrer-Spam.help) but it looks like Google might have actually implemented a fix themselves.
We've been running a spam honeypot account for the last year or so. This is a brand new account, with a brand new UA number (that, crucially, ends in -1 as it appears that the spammers only attack property numbers ending in -1). This account has never been on a website, never been publicly advertised, and never had any legitimate hits sent to it via web, app, or measurement protocol.
We keep this honeypot account to check for new spam sources, but we hadn't checked it for a while. Prompted by a tweet from Simo Ahava, we took a look and it appears that all spam activity stopped on January 29, 2016:
It almost looks as though there are some bits and pieces of experimentation in mid January, which *might* be a test for a fix. Zero spam hits since January 29th, it looks very much like a fix might be implemented.
Some discussion on Twitter suggests that if you have the Exclude Bots option checked, it blocks spam referrals along with all Measurement Protocol hits. You'll find the setting under View Settings:
If this is what's happening, then it's a welcome change -- having an opt-in for the Measurement Protocol means that most users of Universal Analytics, who will likely never need to collect data from anything other than a website, no longer have to worry about lossy data.
We'll update this post if a fix is confirmed.
Update, August 2016: Nobody knows. Referrer spam hasn't gone anywhere, and while some people report disappearing spam referral sources, everyone's mileage varies. We continue to hold out for a solid solution!