Yep, indeed, on doing this:
root@blah-app:/var/log/nginx# grep '23.237.4.26' access.log.1
I discovered many instances of this:
AlphaBot/3.2; +http://alphaseobot.com/bot.html
Found this:
http://www.theinternetofbots.com/list-of-bots/alphabot.html
A bot for collecting data for SEO reports?
So I guess harmless?