Data diddling occurs when someone with access to information of some sort changes this information before it is entered into a computer. This is done to provide some sort of benefit to the data diddler, generally financial, and is a common method of computer-related crime.
Data diddling can occur at various points along the chain of information entry, and it is often very subtle and virtually undetectable. It can be something as small as a time clerk substituting his own name or employee number for another employee's name or number. It can be combated by ensuring that all information is identical, whether it is a hard copy or the data within a digital system.