Does Platform.sh protect against brute force attacks?

No, we don't directly protect against DDoS (Distributed Denial of Service)

For Elite and Enterprise customers, however, the WAF (Web Application Firewall) helps mitigate DDoS amongst other kind of attacks.

We suggest adding a CDN on top of your project to protect against DDoS.

If you need granular control, a WAF that allows for VCL rules that can mitigate attacks and handle large amounts of traffic can be a good option.