In many states sending spam is illegal. Thus, the spammers have techniques to try and ensure that no one knows they sent the spam out to thousands of users at a time. Which of the following best describes what spammers use to hide the origin of these types of e-mails? A. A blacklist of companies that have their mail server relays configured to allow traffic only to their specific domain name. B. Mail relaying, which is a technique of bouncing e-mail from internal to external mails servers continuously. C. A blacklist of companies that have their mail server relays configured to be wide open. D. Tools that will reconfigure a mail servers relay component to send the e-mail back to the spammers occasionally.

In the field of computing, spam refers to unsolicited, repeated e-mails which are sent by malicious users, known as spammers, with the intention of distributing advertisement, propaganda, scams, or luring unsuspected users to malicious websites. Spam is illegal in many states, and spammers can be subject to fines or even prison. Thus, spammers rely on techniques to hide the origin of their spam in order to avoid liability. The most common way to do this is by sending spam through what is known as mail relayers, that is, e-mail servers which are tasked with relaying the e-mail sent to them to other external mail servers. This is done in a very simple way: spammers send an e-mail to the mail relaying service, including a list of e-mail addresses to which said spam mail must be relayed to. The server then relays the e-mail, inadvertenly spamming the mentioned e-mail addresses. In order to avoid this, most mail relayers have tried to implement safeguards, such as requiring users to authenticate themselves before resending any e-mail, and automated systems such as algorithms that learn how to detect spam and block it automatically.