We use AWS Shield Standard, one of AWS's services, to defend against DDoS attacks, as well as implementing API layer protection with AWS WAF and threat detection mechanisms with Amazon GuardDuty.
Teachme Biz uses AWS Fargate as the application execution environment, and OS layer defense is implemented by Amazon Web Services (hereafter referred to as AWS). While we cannot provide details about OS layer defense measures, we use infrastructure that complies with PCI DSS level 1, ISO27001, ISO27017, SOC1, SOC2, SOC3, etc.
In addition, all databases, storage, and mail servers utilize AWS managed services (Amazon Aurora, Amazon S3, Amazon SES), so they are similarly managed by AWS.
For more details, please check the white paper provided by AWS.
https://d1.awsstatic.com/whitepapers/AWS_Fargate_Security_Overview_Whitepaper.pdf