Wikipedia has blocked 381 accounts for what it has called "black hat" editing - charging money for the creation of promotional articles.
The accounts were reportedly run by a "co-ordinated group" of fraudsters who failed to reveal their affiliations.
The investigation, dubbed "Orangemoody" after the first rogue account identified, revealed that the suspect accounts were "sock puppets" - a term that refers to the use of multiple accounts for an improper purpose.
In addition to blocking the 381 "sock puppet" accounts, the editors deleted 210 articles created by them.
Most of the articles, which were related to businesses, business people or artists, were promotional in nature and often included biased or skewed information, unattributed material and potential copyright violations.
The edits made by the accounts were similar enough that investigators believed they were made by one co-ordinated group.
Foundation members Ed Erhart and Juliet Barbara wrote in a blog post: "Neutrality is key to ensuring Wikipedia's quality. Although it does not happen often, undisclosed paid advocacy editing may represent a serious conflict of interest and could compromise the quality of content on Wikipedia.
Not all paid editing is a violation of Wikipedia policies. Museum and university employees around the world edit by disclosing their official affiliations, and several prominent public relations firms have signed an agreement to abide by Wikipedia's paid editing guidelines.
Editing Wikipedia is free and only requires compliance with the project's editorial guidelines.