Table 2.

Following the typology proposed by Saez-Trumper [19] and adding the definitions proposed by Fernquist et al. [27], a description of the most popular mechanisms to spread online misinformation

Type	Technique	Description
Social	Astroturfing	A practice of disguising the sponsors of a message to give the impression that it originated spontaneously, representing the public interest and community concerns.
	Circular reporting	Information, originated by a single source, appearing to come from multiple independent sources and channels with minor modifications.
	Click farms	An operation in which a large group fraudulently interacts with a website to artificially boost internet traffic, deceiving online systems.
	Data voids	Manipulations exploring the lack of natural content to induce search engines to return low-quality and problematic content [28].
	Sock-puppets	The use of false or misleading identities on the Internet to interact with ordinary users on social media for purposes of deception.
	Web brigades	A set of users coordinated to undertake large-scale disinformation campaigns by exploiting the weakness of communities and systems.
Technical	Deepfakes	Manipulations created using deep learning techniques trained on a large number of samples to automatically map facial expressions and to achieve face swapping [29, 30].
	Spam bots	Bots designed to post on online comment sections, spread advertisements, or for extracting contact information for spam mailing lists.
	Social bots	Bots designed to automatically spread messages and advocate ideas, thus influencing public opinion on a given topic. They can also create fake accounts and simulate the popularity of social media profiles (e.g., through a massive network of followers).
Hybrid	Cyborgs	Hybrid accounts combining automatic and human curation. In such accounts, a human periodically takes over a bot account in order to disguise and increase the account’s credibility.
	Sybils	Impersonators who try to connect with a real user’s friends and take advantage of its reputation [31]. Sybils accounts may be operated by bots to spread disinformation and reach a wider audience.