  Social media have become part of modern news reporting, used by journalists
to spread information and find sources, or as a news source by individuals. The
quest for prominence and recognition on social media sites like Twitter can
sometimes eclipse accuracy and lead to the spread of false information. As a
way to study and react to this trend, we introduce {\sc TwitterTrails}, an
interactive, web-based tool ({\tt twittertrails.com}) that allows users to
investigate the origin and propagation characteristics of a rumor and its
refutation, if any, on Twitter. Visualizations of burst activity, propagation
timeline, retweet and co-retweeted networks help its users trace the spread of
a story. Within minutes {\sc TwitterTrails} will collect relevant tweets and
automatically answer several important questions regarding a rumor: its
originator, burst characteristics, propagators and main actors according to the
audience. In addition, it will compute and report the rumor's level of
visibility and, as an example of the power of crowdsourcing, the audience's
skepticism towards it which correlates with the rumor's credibility. We
envision {\sc TwitterTrails} as valuable tool for individual use, but we
especially for amateur and professional journalists investigating recent and
breaking stories. Further, its expanding collection of investigated rumors can
be used to answer questions regarding the amount and success of misinformation
on Twitter.
