Carbon Fraud is an aspect of global carbon markets.
Basically due to weak certification and validation processes in carbon markets, it is often quite easy to operate a 'fake' carbon offsetting business; i.e. claiming to run an offshore forest preservation scheme generating carbon credits when no such thing exists in reality (i.e. just pocket the money).
Also, due to the difficult nature of assessing exactly how much carbon some scheme or process offsets, you can also get fraud through over estimating the amount of carbon offset.
It is understood in some regions that organized crime has got involved in carbon markets, and that some markets have had to be suspended to investigate systematic fraud.