At least two of the eight first-round groups of four produced tough obstacles for their participants to progress to the knockout rounds.
The rankings were prepared after examining the volume of terrorist and rebel alerts, messaging traffic, videos, photos, incidents and the number of killed and injured in a country over the past 30 days.
An inspired performance from Douglas Costa helped Brazil to a 3-0 win over Peru on Tuesday and lifted them into third place in the South American qualifying group for the 2018 World Cup in Russia.
Switzerland struck twice in quick succession to stun Euro 2016 champions Portugal 2-0 in a World Cup qualifier on Tuesday and hand them a first competitive defeat in two years under coach Fernando Santos.
Images from the Champions League matches played across Europe on Wednesday.
