As each ESP connects to the PSN, weakness associated with the ESP's telecommunications networks and services will insert vulnerabilities into the PSN. Delimitation of the scope of access to the PSN is necessary to prevent ESP employees from gaining unauthorized access to PSN services.
Each carrier must provide a method for ESPs to access telecommunications systems and facilities. It is a concern to what degree a carrier will investigate the credentials of an ESP, as well as the degree of security provided by the ESP, before allowing the ESP access to the PSN. It is possible for malicious hackers to take on the appearance of an ESP to obtain access to the PSN.