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Email spam, also known as junk email or unsolicited bulk email (''UBE''), is a subset of electronic spam involving nearly identical messages sent to numerous recipients by email. The messages may contain disguised links that appear to be for familiar websites but in fact lead to phishing web sites or sites that are hosting malware. Spam email may also include malware as scripts or other executable file attachments. Definitions of spam usually include the aspects that email is unsolicited and sent in bulk. One subset of UBE is ''UCE'' (unsolicited commercial email). The opposite of "spam", email which one wants, is sometimes called "ham". Like other forms of unwanted bulk messaging, it is named for Spam luncheon meat by way of a Monty Python sketch in which Spam is depicted as ubiquitous and unavoidable.〔(【引用サイトリンク】publisher=Merriam-Webster )〕 Email spam has steadily grown since the early 1990s. Botnets, networks of virus-infected computers, are used to send about 80% of spam. Since the expense of the spam is borne mostly by the recipient,〔 it is effectively postage due advertising. The legal status of spam varies from one jurisdiction to another. In the United States, spam was declared to be legal by the CAN-SPAM Act of 2003 provided the message adheres to certain specifications. ISPs have attempted to recover the cost of spam through lawsuits against spammers, although they have been mostly unsuccessful in collecting damages despite winning in court. Spammers collect email addresses from chatrooms, websites, customer lists, newsgroups, and viruses which harvest users' address books, and are sold to other spammers. They also use a practice known as "email appending" or "epending" in which they use known information about their target (such as a postal address) to search for the target's email address. Much of spam is sent to invalid email addresses. According to the Message Anti-Abuse Working Group, the amount of spam email was between 88–92% of email messages sent in the first half of 2010. ==Overview== From the beginning of the Internet (the ARPANET), sending of junk email has been prohibited. Gary Thuerk sent the first email spam message in 1978 to 600 people. He was reprimanded and told not to do it again. 〔(Opening Pandora's In-Box ). 〕 The ban on spam is enforced by the Terms of Service/Acceptable Use Policy (ToS/AUP) of internet service providers (ISPs) and peer pressure. Even with a thousand users junk email for advertising is not tenable, and with a million users it is not only impractical,〔(【引用サイトリンク】title=alt.spam FAQ )〕 but also expensive.〔(【引用サイトリンク】title=Why is spam bad? )〕 It was estimated that spam cost businesses on the order of $100 billion in 2007.〔(Ferris Research: Cost of Spam )〕 As the scale of the spam problem has grown, ISPs and the public have turned to government for relief from spam, which has failed to materialize.〔(Spam's Cost To Business Escalates )〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Email spam」の詳細全文を読む スポンサード リンク
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