Spam blogs, sometimes referred to by the neologism splogs, are artificially created weblog sites which the author uses to promote affiliated websites or to increase the search engine rankings of associated sites. The purpose of a splog can be to increase the PageRank or backlink portfolio of affiliate websites, to artificially inflate paid ad impressions from visitors, and/or use the blog as a link outlet to get new sites indexed. Spam blogs are usually a type of scraper site, where content is often either inauthentic text or merely stolen (see blog scraping) from other websites. These blogs usually contain a high number of links to sites associated with the splog creator which are often disreputable or otherwise useless websites.
There is frequent confusion between the terms "splog" and "spam in blogs". Splogs are blogs where the articles are fake, and are only created for search engine spamming. To spam in blogs, conversely, is to include random comments on the blogs of innocent bystanders, in which spammers take advantage of a site's ability to allow visitors to post comments that may include links.
The term may be applied to more recent infections, most noticably those reported by Webtrends in April 2008. Leveraging botnets, spammers have infected several thousand pages which display prominent keywords from the Google Trends site by bypassing the CAPTCHA authentication method, which had previously subdued all spam bloggers. A recent sighting puts the top ten google hottest terms of the day as all being owned by spambots on the Blog Results page. As they have gone mostly unchecked, they have also infected real SERP Page One web results and corrupt any hot search terms more than a month old. Phraseoligist reports that the attacks appear on AOL Journal, Blogspot and Spaces Live. Hackers are using a number of methods including link farming, spamdexing and keyword stuffing each in a simple, moderated form to achieve top PageRank results. Most of the sites contain an animated graphic which appears as a youtube streaming video. Once clicked, users become infected with one of several variants of spyware. This generates revenue for the spambot's owner.
Google's search engine uses PageRank, which is susceptible to link flooding, especially from highly weighted bloggers. One splog clearly states: "Google's run by people who can't be bothered to post links on the internet." Splogs could become a detractor to people using, enjoying and finding value in the blogosphere. Splogs sometimes choose a name similar to a popular blog in order to benefit from the occasional incoming link from careless bloggers, who think they are linking to the popular site.
Splog activity can cause problems for legitimate bloggers, if search engines respond to splog by blocking or treating as 'suspicious' all web addresses in a particular domain.
On February 24, 2007, Splog Reporter announced on its website that it would no longer be providing a splog reporting service.