We have noticed an unusually large percentage of traffic coming from sources like "referral / 4000" (it is not actually 4000, the number is more specific but in the 4000's, I don't want to be more specific unless I have to in case it is a breach of confidentiality). Sometimes there are multiple "referral / 4000" with slightly different numbers simultaneously. They account for upwards of 25% of all traffic and always result in 0 conversions. We have several other websites that do not show this traffic source.
I have performed every google search I could come up with and so has the rest of my team.
Has anybody ever encountered a similar situation?