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Spam Filter Expert >> What is Spam >> What is Email Spam
What is Email Spam?
E-mail spam is the most common form of Internet spamming. It involves sending unsolicited commercial messages to recipients in bulk. Unlike legitimate commercial e-mail, spam is generally sent without the explicit permission of the recipients, and frequently contains various tricks to bypass e-mail filtering.
Spammers obtain e-mail addresses in a number of ways. The most common are harvesting addresses from Usenet postings, Web pages or DNS listings. The will also frequently guess common names at known domains (known as a dictionary attack). Many spammers utilize programs called web spiders to find e-mail addresses on web pages.
Spammers go to great lengths to conceal the origin of their messages usually using spoof e-mail addresses. Spammers will often modify the e-mail message so it looks like it is coming from another e-mail address. Spammers try to circumvent the email filters by intentionally misspelling common spam filter trigger words. For example, "viagra" might become "vaigra", or other symbols may be inserted into the word as in "v/i/a/g./r/a". Spam filtering systems and service providers have begun to use the misspellings themselves as a filtering test.
The most dedicated spammers are making a great deal of money and are often one step ahead of the anti spam services in what has become the Internet equivalent of an arms race. Retail e-mail services are updated constantly with improved spam filters, keeping track of spammers' technological progress by examining e-mails their users report as spam (many providers today have a prominent button to report spam).
Many spammers create and distribute trojans or viruses that render an unprotected PC a "zombie computer"; the zombie will inform a central unit of its existence, and the central unit will command the "zombie" to send a low volume of spam. This allows spammers to send high volumes of e-mail without being caught by their ISPs or being tracked down by antispammers; a low volume of spam is instead sent from many locations simultaneously.
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