Does it matter? Just spam ban them and be done with it.
If there's high volumes of posts from a specific IP address or user, it's likely a bot. If it's actually on topic spam - it's likely a person. Spam cleaner cleans them both up just as well
Yeah knew that. My site having this same sort of spamming - short articles with site links just after moving to xf last 3 months ago. Haven’t got any problem previously with vb as we also use the same stopforumspam feature.