Get your web applications, APIs and other web-based assets thoroughly tested for security issues via a combination of manual assessments and automated scanning.
This testing can be done in a black-box, grey-box, or white-box fashion. Black-box testing would involve assuming the position of an malicious actor with no prior knowledge of inner workings, no access to source code or internal documentation, and no privileges other than what could normally be obtained by external users. White-box testing is the opposite, where we would be provided with unrestricted access to source code, documentation, various levels of privileges/permissions. Grey-box engagements fall somewhere in the middle and can be adapted to your needs and willingness to provide internal information.
Engagements generally last one to several weeks, depending on the complexity of your application.