Manual code review is an optional task in the SDL and is usually performed by highly skilled individuals on the application security team and/or the security advisor. While analysis tools can do much of the work of finding and flagging vulnerabilities, they are not perfect. As a result, manual code review is usually focused on the “critical” components of an application. Most often it is used where sensitive data, such as personally identifiable information (PII), is processed or stored. It is also used to examine other critical functionality such as cryptographic implementations.