Spam filtering techniques
Unethical e-mail senders bear little or no cost for mass distribution of messages, yet normal e-mail users are forced to spend time and effort purging fraudulent and otherwise unwanted mail from their mailboxes. In this article, I describe ways that computer code can help eliminate unsolicited commercial e-mail, viruses, trojans, and worms, as well as frauds perpetrated electronically and other undesired and troublesome e-mail. In some sense, the final and best solution for eliminating spam will probably take place on a legal level. In the meantime, however, you can do some things from a code perspective that can serve as an interim solution to the problem, until (if ever) the laws begin to evolve at the same rate as public frustration.
Considering matters technically -- but also with common sense -- what is generally called "spam" is somewhat broader than the category "unsolicited commercial e-mail"; spam encompasses all the e-mail that we do not want and that is only very loosely directed at us. Such messages are not always commercial per se, and some push the limits of what it means to be solicited. For example, we do not want to get viruses (even from our unwary friends); nor do we generally want chain letters, even if they don't ask for money; nor proselytizing messages from strangers; nor outright attempts to defraud us. In any case, it is usually unambiguous whether a message is spam, and many, many people get the same such e-mails.
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