In general, search engine optimisation can be regarded as a 'positive' enterprise - not necessarily in any moral sense, but in the sense that it relies upon buoying up one particular website or webpage within the search engine results. Although other websites or pages may go down in the results as a result of this positive shift, regular search engine optimisation does not directly harm other websites.
However, the system within which search engine optimisation operates is also equipped to penalise certain websites for breaking particular rules. In some ways, this is an inevitable consequence of the system. Without the means to penalise websites for breaking the rules, there would be no point in having rules in the first place. For this reason, search engine operators devised a number of different penalties that could be assigned to miscreant websites according to the severity of their offence.
As you might expect, 'negative' search engine optimisation is essentially the opposite of the positive, buoyant effect described earlier. This is when an individual or business with the relevant expertise decides to embark upon a cyber-smear campaign, forcing the website of an enemy or competitor down through the search engine results page rankings or even out of search engine indexes altogether. It should go without saying that this is unethical, underhanded and unsportsmanlike in the extreme.
One example of negative search engine optimisation is when an attacker initiates a 'denial of service' attack on the website of their victim. This generally forces the website to crash. Once the website is down, the attacker can follow-up by using various techniques in order to encourage search engine web crawlers to visit the site. When crawlers visit a website and find that it is completely gone, their respective search engines will often de-index that site.
Another way in which practitioners perform negative SEO is by associating the website of a victim with a 'bad neighbourhood' domain in which they have a controlling influence. Under the 'bad neighbourhood' system, sites that are heavily linked into networks of illicit pharmaceuticals retailers and other dubious websites are tarred with the 'bad neighbourhood' brush and may experience ranking penalties or even complete de-indexing. One way in which attackers are able to associate victims' sites with these bad neighbourhoods is by redirecting web users from a bad neighbourhood URL to the URL of the victim's website. Search engines often pick up on this kind of activity quickly, and will often assume the victim is involved and penalise them accordingly.
Although negative search engine optimisation can be a tempting proposition for many businesses, it is unprofessional conduct and can seriously tarnish the reputation of an otherwise successful enterprise. For moral reasons and in order to preserve the reputation of the company concerned, negative SEO should never be employed. If you think your own website may have been the victim of a negative SEO attack, you should inform search engine operators as soon as possible after the event so they can begin taking steps to restore your site to their indexes.
