We have implemented DDoS attack protection using AWS Shield Standard, one of AWS's services, as well as API layer protection via AWS WAF and threat detection mechanisms through Amazon GuardDuty.
Teachme Biz uses AWS Fargate and Amazon EKS Auto Mode as the application execution environment. OS layer protection is handled by Amazon Web Services (hereinafter referred to as "AWS"), so we are unable to provide answers regarding OS layer protection measures on our end. However, we utilize infrastructure that complies with PCI DSS Level 1, ISO27001, ISO27017, SOC1, SOC2, SOC3, and other standards.
In addition, our databases, storage, and mail servers all make use of AWS managed services (Amazon Aurora, Amazon S3, and Amazon SES), and are therefore managed by AWS in the same manner.