Web hosts and website operators have responded by banning spammers, leading to an ongoing struggle between them and spammers in which spammers find new ways to evade the bans and anti-spam programs, and hosts counteract these methods.
E-mail spambots harvest e-mail addresses from material found on the Internet in order to build mailing lists for sending unsolicited e-mail, also known as spam.
Such spambots are web crawlers that can gather e-mail addresses from websites, newsgroups, special-interest group (SIG) postings, and chat-room conversations.
A number of programs and approaches have been devised to foil spambots.
One such technique is address munging, in which an e-mail address is deliberately modified so that a human reader (and/or human-controlled web browser) can interpret it but spambots cannot.
This has led to the evolution of more sophisticated spambots that are able to recover e-mail addresses from character strings that appear to be munged, or instead can render the text into a web browser and then scrape it for e-mail addresses.
Alternative transparent techniques include displaying all or part of the e-mail address on a web page as an image, a text logo shrunken to normal size using inline CSS, or as text with the order of characters jumbled, placed into readable order at display time using CSS.
Forum spambots surf the web, looking for guestbooks, wikis, blogs, forums, and other types of web forms that it can then use to submit bogus content. Some spam messages are targeted towards readers and can involve techniques of target marketing or even phishing, making it hard to tell real posts from the bot generated ones.