You can find a few feeds in the right menu under the "DDoS" section and search the blog with keyword "DDoS".
The links below are for vendors do not provide RSS feed service, or our aggregator has problem parsing the vendor's feed. However, I still have record here to support my knowledge.
Radware
Here's the link of Radware's blog content.
DDoS Threats & Security Attacks: DDoS Reports & Security Threats (radware.com)