Brightmail, a vendor of e-mail filters and anti-spam applications warned that close to 5 million spam "attacks" or "bursts" occurred in June 2002 and that spam has mushroomed 450 percent since June 2001. This pace continued unabated well into the beginning of 2004 when the introduction of spam filters began to take effect. PC World concurs. Between one half and three quarters of all e-mail messages are spam or UCE (Unsolicited Commercial Email) - unsolicited and intrusive commercial ads, mostly concerned with sex, scams, get rich quick schemes, financial services and products, and health articles of dubious provenance. The messages are sent from spoofed or fake e-mail addresses. Some spammers hack into unsecured servers - mainly in China and Korea - to relay their missives anonymously. Starting in 2003, malicious hackers began using spam to install malware - such as viruses, adware, spyware, and Trojans - on the unprotected personal computers of less savvy users. They thus transform these computers into "zombies", organize them into spam-spewing "bots" (networks), and sell access to them to criminals on penumbral boards and forums all over the Net. Spam is an industry. Mass e-mailers maintain lists of e- mail addresses, often "harvested" by spamware bots - specialized computer applications - from Web sites. These lists are rented out or sold to marketers who use bulk mail services. They come cheap - c. $100 for 10 million addresses. Bulk mailers provide servers and bandwidth, charging c. $300 per million messages sent. As spam recipients become more inured, ISPs less tolerant, and both more litigious - spammers multiply their efforts in order to maintain the same response rate. Spam works. It is not universally unwanted - which makes it tricky to outlaw. It elicits between 0.1 and 1 percent in positive follow ups, depending on the message. Many messages now include HTML, JavaScript, and ActiveX coding and thus resemble (or actually contain) viruses and Trojans. Jupiter Media Matrix predicted in 2001 that the number of spam messages annually received by a typical Internet user will double to 1400 and spending on legitimate e- mail marketing will reach $9.4 billion by 2006 - compared to $1 billion in 2001. Forrester Research pegs the number at $4.8 billion in 2003. More than 2.3-5 billion spam messages are sent daily. eMarketer puts the figures a lot lower at 76 billion messages in 2002. By 2006, daily spam output will soar to c. 15 billion missives, says Radicati Group. Jupiter projects a more modest 268 billion annual messages this year (2005). An average communication costs the spammer 0.00032 cents. PC World quotes the European Union as pegging the bandwidth costs of spam worldwide in 2002 at $8-10 billion annually. Other damages include server crashes, time spent purging unwanted messages, lower productivity, aggravation, and increased cost of Internet access.