"Statement on
Auditing Standards (SAS) No. 70, Service Organizations, is an
auditing standard developed by the American Institute of Certified
Public Accountants (AICPA). SAS 70 is the authoritative guidance
that allows service organizations to disclose their control
activities and processes to their customers and their customers'
auditors in a uniform reporting format. SAS 70 is a widely
recognized standard, because it signifies that a service
organization has had its control objectives and control activities
examined by an independent accounting and auditing firm. A formal
report including the auditor's opinion ("Service Auditor's
Report") is issued to the service organization at the
conclusion of a SAS 70 examination."
Source: www.sas70.com.