Like a virus, viral marketing is the method by which something is communicated from one user to another. But unlike the act of a virus, viral marketing tools are not intended to destroy, change, or violate the rights of computer.

Viral Marketing is simply the act of marketing a message that can be passed along to others until it has been passed to an exponentially large amount of people. Like a virus, the strategy is for the message to reach and knowingly become distributed by the recipient to friends, family and network of associates.

To be effective, Viral Marketing has to be tailored to its target audience. For instance, it should exploit common interests and behaviors of the recipient and should be effortless to pass along to another party. And, in order to maximize its reach, its necessary to ensure that it is lightweight and cross-platform enabled. Here is a classic example of a viral marketing strategy:

Yahoo! Dial

New members sign-up
They send e-mails to friends and entire network of other individuals.
Yahoo! Mail inserts the following at the bottom of an e-mail and each user would see something similar to this:

Do You Yahoo!?

New! SBC Yahoo! Dial - 1st Month Free & unlimited access

While continuing to e-mail to friends, family and others, the marketing message begins to communicate to a growing population of e-mail users.