An Application Security Developer is responsible for implementing, maintaining, and improving security measures within applications. They work on building secure software from the initial design phase, integrating security protocols during the development phase, and conducting security testing before deployment. Their tasks include identifying vulnerabilities, developing patches, and creating automated security tests. They also ensure compliance with data protection regulations. They work closely with other developers to integrate security considerations in the programming process. Additionally, they provide training and guidance to other team members about best practices in application security.