<p>Disinformation spread through social networks is a growing global problem that may have a serious impact on public health issues. Therefore, a growing line of research is emerging to unravel the social influence strategies used in fake news and disinformation campaigns. In this investigation, we exposed participants to a set of stimuli that simulate real tweets. Our aim was to assess the proneness of people to share them and to carry out fact-checking before doing so, together with the degree of belief in the veracity of the information. We focused on the differences in the way people react to tweets involving manipulation techniques in comparison with those which do not, and on the possible effects of an online campaign for the prevention of the spreading of disinformation and the promotion of fact checking. Our results show that people tend to consider as more accurate the stimuli that just present neutral information than those that involve any strategy of influence. The effects of the online campaign translated in the experimental group assuming a lower accuracy of the items regardless of their manipulation. After the intervention, the fact-checking of non-manipulated items increased significantly in the experimental group, whereas the predisposition to share any information decreased. Based on these results, we can conclude that people are more prone to share non-manipulated information and consider those items to be more truthful. A nonspecific warning campaign can reduce the general tendency of people to share and believe social media information, regardless of its accuracy.</p>