There is no violent crime in Taman Negara. As anywhere, do not leave valuables lying around unguarded. Beware of theft from hotel rooms and always monitor and secure your belongings
Wear footwear when outside. If you make a jungle trek on your own inform the park headquarters where you are going and at what time you will be back. People sometimes get lost or disoriented in the jungle.
Leeches are common in the park but are not as dangerous as they are made out to be. They're fairly annoying although after a few days you'd get used to them.
