For the past week or so, I've been getting a series of Pingbacks from a spam blog that reposts a blog post a couple times a day as a new post each time. It's up to about 220 copies of the post, each one having sent me a Pingback, and each one showing up in my reader as a notification, which also causes it to be sent to my phone.

Since I use webmention.io to handle my incoming Webmentions (and Pingbacks), this would be the best place to block the site, rather than filtering it out in my reader or my website.
Webmention.io previously had no way to actually completely block a domain. As Webmentions have started growing in popularity, it's become obvious that we need more tools to combat spam and abuse. While this site was actually sending me Pingbacks, the same applies to Webmentions.
Today I added a new feature to webmention.io to allow people to entirely block a domain, and delete any webmentions received from that domain.

From the dashboard, you can click the "X" on any recent webmention, or you can paste a URL from one you've received in the past. You'll be taken to this screen where you can either delete just the one webmention, or entirely block the domain.
Once you've blocked the domain, it will show up in your blocklists page!

I hope this helps others keep out spam as well! I'm sure looking forward to never seeing that notification on my phone again!