Cisco SPA100 Series Analog Telephone Adapters are prone to an information-disclosure vulnerability. An attacker can exploit this issue to gain access to sensitive information that may aid in further attacks. This issue is being tracked by Cisco Bug ID CSCvq50520.
Block external access at the network boundary, unless external parties require service.
If global access isn't needed, filter access to the affected computer at the network boundary. Restricting access to only trusted computers and networks might greatly reduce the likelihood of successful exploits.
Deploy network intrusion detection systems to monitor network traffic for malicious activity.
Deploy NIDS to monitor network traffic for signs of anomalous or suspicious activity such as unexplained incoming and outgoing traffic. This may indicate exploit attempts or activity that results from successful exploits.
Updates are available. Please see the references or vendor advisory for more information.