Definition of Malfeasance
Malfeasance is the act of wrong doing or evil conduct. Malfeasance should not be confused with misfeasance which is the legal act of not performing something correctly or making a mistake. Nonfeasance is the failure to perform one's duty or take appropriate action.
Malfeasance generally is used in regards to a public official and their failure to perform their job or acting inappropriately with malicious intent. Keep in mind, malfeasance must have interfered with the official performing their official duties. This can, however, be difficult for the courts to prove. If it is proven the public official can be removed from their job.
A good example was the 2013 IRS scandal. If it is proven that the top IRS officials specifically targeted political groups to impede their ability to get a tax-exempt status this could be malfeasance.If, however, the courts decide this effort was the misguided actions of a few low level staff agents who made a mistake, this could be misfeasance.