Scumware generally arrives in the form of a Web browser plug-in, which intercepts Web pages that a surfer is viewing, contacts the scumware's creator's server, and inserts advertising links into the body of the page, which then corrupt the site as viewed by the surfer. The unwelcome ads can be in the form of banner ads covering the ads normally shown on the site, or links created from words in the site's text, including hijacking internal, external, and ad links, and redirecting them. The links can potentially lead to "adult," gambling, or other sites of which the owner of the altered/hijacked site may strongly disapprove, and would not link to willingly. The revenue (generally CPC) from those ads goes to the scumware provider, without any compensation to the owners of the sites being visited/altered. Scumware plug-ins can be surreptitiously included in unrelated software downloads, such as Gator and KaZaa.

Here are some sites discussing and opposing scumware...

Here are some scumware perpetrators...