I use the Analyics filters. I did start by using the Referral Exclusion List, but another article on this advises against this.
BAD Advice: Use The Referral Exclusion List
A number of sites recommend using the Referral Exclusion list feature (Admin – Property – Tracking Info) — this does NOT work! While it may remove some of the annoying entries in your referral report, it may actually change the session to a Direct visit and it continues to appear in your reports.
I was getting a lot of obviously spam, direct referrals one one site, and this may be the reason. Being labelled as direct, there is no way to filter them without removing all direct traffic.
I have now cleared the exclusion list, but will have to wait and see if it works.