Similar to how a DNS server caches the addresses of accessed websites, a proxy server caches the contents of those websites and handles the heavy lifting of access and retrieval for users. Proxy servers can also maintain a list of blacklisted and whitelisted websites so as to prevent users from getting easily preventable infections. Depending on the intentions of the company, Proxy servers can also be used for monitoring web activity by users to make sure that sensitive information is not leaving the building. Proxy servers also exist as Web Proxy servers, allowing users to either not reveal their true access point to websites they are accessing and/or getting around region blocking.