Email Address Harvesting - Methods

Methods

The simplest method involves spammers purchasing or trading lists of email addresses from other spammers.

Another common method is the use of special software known as "harvesting bots" or "harvesters", which spider Web pages, postings on Usenet, mailing list archives, internet forums and other online sources to obtain email addresses from public data.

Spammers may also use a form of dictionary attack in order to harvest email addresses, known as a directory harvest attack, where valid email addresses at a specific domain are found by guessing email address using common usernames in email addresses at that domain. For example, trying alan@example.com, alana@example.com, alanb@example.com, etc. and any that are accepted for delivery by the recipient email server, instead of rejected, are added to the list of theoretically valid email addresses for that domain.

Another method of email address harvesting is to offer a product or service free of charge as long as the user provides a valid email address, and then use the addresses collected from users as spam targets. Common products and services offered are jokes of the day, daily bible quotes, news or stock alerts, free merchandise, or even registered sex offender alerts for one's area. Another technique was used in late 2007 by the company iDate, which used email harvesting directed at subscribers to the Quechup website to spam the victim's friends and contacts.

Spam differs from other forms of direct marketing in many ways, one of them being that it costs little more to send to a larger number of recipients than a smaller number. For this reason, there is little pressure upon spammers to limit the number of addresses targeted in a spam run, or to restrict it to persons likely to be interested. One consequence of this fact is that many people receive spam written in languages they cannot read — a good deal of spam sent to English-speaking recipients is in Chinese or Korean, for instance. Likewise, lists of addresses sold for use in spam frequently contain malformed addresses, duplicate addresses, and addresses of role accounts such as postmaster.

Spammers may harvest email addresses from a number of sources. A popular method uses email addresses which their owners have published for other purposes. Usenet posts, especially those in archives such as Google Groups, frequently yield addresses. Simply searching the Web for pages with addresses — such as corporate staff directories or membership lists of professional societies — using spambots can yield thousands of addresses, most of them deliverable. Spammers have also subscribed to discussion mailing lists for the purpose of gathering the addresses of posters. The DNS and WHOIS systems require the publication of technical contact information for all Internet domains; spammers have illegally trawled these resources for email addresses. Spammers have also concluded that generally, for the domain names of businesses, all of the email addresses will follow the same basic pattern and thus are able to accurately guess the email addresses of employees whose addresses they have not harvested. Many spammers use programs called web spiders to find email addresses on web pages. Usenet article message-IDs often look enough like email addresses that they are harvested as well. Spammers have also harvested email addresses directly from Google search results, without actually spidering the websites found in the search.

Spammer viruses may include a function which scans the victimized computer's disk drives (and possibly its network interfaces) for email addresses. These scanners discover email addresses which have never been exposed on the Web or in Whois. A compromised computer located on a shared network segment may capture email addresses from traffic addressed to its network neighbors. The harvested addresses are then returned to the spammer through the bot-net created by the virus.

A recent, controversial tactic, called "e-pending", involves the appending of email addresses to direct-marketing databases. Direct marketers normally obtain lists of prospects from sources such as magazine subscriptions and customer lists. By searching the Web and other resources for email addresses corresponding to the names and street addresses in their records, direct marketers can send targeted spam email. However, as with most spammer "targeting", this is imprecise; users have reported, for instance, receiving solicitations to mortgage their house at a specific street address — with the address being clearly a business address including mail stop and office number.

Spammers sometimes use various means to confirm addresses as deliverable. For instance, including a hidden Web bug in a spam message written in HTML may cause the recipient's mail client to transmit the recipient's address, or any other unique key, to the spammer's Web site. Users can defend against such abuses by turning off their mail program's option to display images, or by reading email as plain-text rather than formatted.

Likewise, spammers sometimes operate Web pages which purport to remove submitted addresses from spam lists. In several cases, these have been found to subscribe the entered addresses to receive more spam.

When persons fill out a form it is often sold to a spammer using a web service or http post to transfer the data. This is immediate and will drop the email in various spammer databases. The revenue made from the spammer is shared with the source. For instance if someone applies online for a mortgage, the owner of this site may have made a deal with a spammer to sell the address. These are considered the best emails by spammers, because they are fresh and the user has just signed up for a product or service that often is marketed by spam.