Yes, there could be an attack on the Rio Olympics by ISIS. An attack is always a possibility, especially with the volume of people attending an international event like the Olympics. Also, the "lone wolf" phenonemenon makes it possible for even one person to cause destruction inspired by or on behalf of ISIS. The hope is that intelligence will help to idenitfy any possible threats and thwart any attack before it happens, and Olympic security will be effective in handling the crowds and keeping everyone safe.
As we've seen over and over again-- in Paris, in Orlando, and around the world-- any large gathering is a potential target for an ISIS attack. Brazil's current political instability only adds to the possibility of terrorists' focusing in on the Olympics as a place for violence. Heightened security is a must at global events such as the Olympics.
Yes, there is a threat of attack at the Rio Olympics by the group ISIS. In the two years since the declared creation of ISIS there have been over 70 attacks in Asia, North Africa, Australia, North America, Middle East and Europe. ISIS group leader Maxime Hauchard tweeted last year “Brazil, you are our next target” as this is a global world stage, the chance of an attack is imminent.
The possibility of an attack on the Rio Olympics by ISIS is quite high. Brazil was threatened as early as November 2015. Reports also suggest that there is an increase in the number of ISIS supporters in Brazil. Several measures are being taken to curb such an attack according to Brazil’s anti-terror chief.