A spam-bot (short for spam robot) is a computer program that retreives email addresses from websites, These email addresses are then added to mailing lists used for marketing and advertising purposes.
Unsolicited commercial email (or ‘spam’ as it is commonly known) is email, typically of a marketing or nefarious intent, not requested by the recipient.
With the advent of online journals (blogs) new forms of spam have emerged:
submission of marketing-related content to blog postings, often automated
using an HTTP header to mimic a referring link from an advertising website to the target website; if the target website publishes a list of the top referring sites it linking to the advertising website (and so increase the search engine ranking of the advertiser’s website)
The New Zealand Government has introduced legislation that expands the definition of spam:
…email, instant messaging, SMS and MMS (text and image-based mobile phone messaging) of a commercial nature. It does not cover faxes, Internet pop-ups or voice telemarketing. 
The Act comes into effect from the 5th September 2007, and provides a framework for:
This Bill aims to prohibit the sending of unsolicited electronic messages of a marketing nature (email, text messages, or instant messages) and provide a legislative basis to combat the growth of spam.