BizTalk Server 2006 Security and Protection
Microsoft BizTalk Server 2006 can help protect and secure your BizTalk applications and data by authenticating the sender of a message and authorizing the receiver of a message. BizTalk Server uses access control and least rights to limit access, and provides integrated security through Enterprise Single Sign-On. You can further enhance BizTalk Server security by deploying IPSec Tunneling, SSL, and certificate services (included with Microsoft Windows Server 2003) and strong encryption, security context switching and impersonation, and integrated key management (provided by Microsoft SQL Server 2005).
Resources in the BizTalk Server Documentation