Colombia has made great improvements with internal security within the past 10 years. The rebel forces have almost entirely been disbanded. It is now safe to travel to almost any part of the country, which would have been unheard of 10 years ago.
Having said that, a traveler to Colombia must be cautious of things like petty theft, pickpockets, and people stealing things from hotel rooms.
There is corruption and crime, but the tourist are mostly looked after by the police. Foreigners usually get more help from the authorities than regular Colombians. Tourism is encouraged and anything that detracts from the industry is discouraged.
Rebels from the past.