Generally speaking, Vietnam is a very safe destination for visitors. Muggings and street robberies are rare, but you should still use common sense and hide valuable items and large amounts of money. As you might expect, most taxi touts and fake tour guides hang around the big hotels in cities like Hanoi. Just ignore them. Road traffic accidents are probably one of the biggest risks you will face, so stay away from the temptation of riding on a motorbike. In less-visited areas, there is also the risk of unexploded ordinance from the Vietnam War. Only walk where you know it is safe to do so. Find more information here.