Subject Information Access: In digital certificates, an extension that specifies a method to retrieve information about the owner of a certificate and a name to indicate where to locate it.

If a certificate that has the subject information access (SIA) extension is installed on a Windows Vista Service Pack 1 (SP1)-based computer or on a Windows Server 2008-based computer, applications that involve certificate validation become very slow. For example, you may experience a delay of 2 to 5 minutes when you visit a secure Web site or when you verify a file signature.