Image: Getty

Twitter, Spotify and Reddit, and a huge swath of other websites were down or screwed up this morning. This was happening as hackers unleashed a large distributed denial of service (DDoS) attack on the servers of Dyn, a major DNS host. It's probably safe to assume that the two situations are related.

Domain Name Servers (DNS) act as the Internet's phone book. Basically, they facilitate your request to go to a certain webpage and make sure you are taken to the right place. If the DNS provider that handles requests for Twitter is down, well, good luck getting to Twitter. Some websites are coming back for some users, but it doesn't look like the problem is fully resolved.

Dyn posted this update on its website: "Starting at 11:10 UTC on October 21th-Friday 2016 we began monitoring and mitigating a DDoS attack against our Dyn Managed DNS infrastructure. Some customers may experience increased DNS query latency and delayed zone propagation during this time. Updates will be posted as information becomes available."

Here's a list of websites that readers have told us they are having trouble accessing:

ActBlue

Basecamp

Big cartel

Box

Business Insider

CNN

Cleveland.com

Esty

Github

Grubhub

Guardian.co.uk

HBO Now

Iheart.com (iHeartRadio)

Imgur

Intercom

Intercom.com

Okta

PayPal

People.com

Pinterest

Playstation Network

Recode

Reddit

Spotify

Squarespace Customer Sites

Starbucks rewards/gift cards

Storify.com

The Verge

Twillo

Twitter

Urbandictionary.com (lol)

Weebly

Wired.com

Wix Customer Sites

Yammer

Yelp

Zendesk.com

Zoho CRM

Here's an internet outage map from Level3:

At the time of publication Dyn said that it was still dealing with the problem.

What websites are down for you? Send a tip to [email protected]

Update 9:05 AM EST: Judging by emails from readers, this problem seems to be getting worse.

This story is updating…