We have implemented protection against DDoS attacks using AWS Shield Standard, one of AWS's services, along with API layer protection via AWS WAF and threat detection mechanisms through Amazon GuardDuty.
Teachme Biz uses AWS Fargate as its application execution environment, and OS layer defense is handled by Amazon Web Services (hereinafter referred to as "AWS"). Therefore, we are unable to provide responses regarding OS layer defense measures from 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 leverage AWS managed services (Amazon Aurora, Amazon S3, and Amazon SES), and are similarly managed by AWS.