Salesforce has identified the cause as an issue with their third-party DNS provider. Salesforce is working urgently to resolve this and will provide information as they learn more.
Salesforce login may or may not be successful. If login works, users may experience intermittent connectivity issues and may see blank pages while navigating Salesforce applications. WPI Information Technology system administrators are monitoring the issue closely, and will provide updates when available from Salesforce.
Status updates can be viewed at Salesforce Help (Related Action).