Krebs on Security: Where Did That Scammer Get Your Email Address?

‘Some of the more prolific spammers rely on bots that crawl millions of Web sites and “scrape” addresses from pages. Others turn to sellers on underground cybercrime forums. Additionally, there are a handful of open-air markets where lists of emails are sold by the millions. If you buy in bulk, you can expect to pay about a penny per 1,000 addresses.’