Although Germany's east is considered to be a bit more dangerous for people "looking foreign" this is not problem in Jena due to the high number of foreigners, especially foreign students. Jena is amongst the towns with the highest ratio of foreigners in eastern Germany. So just take those measures you would normally take in the town you come from.Though, when using the tram in the night, the risk of encountering people you didn't want to encounter rises.
