It refers to the alteration of the existing data , most often seen before it is entered into an application.This type of crime is extremely common and can be prevented by using appropriate access controls and proper segregation of duties. It will more likely be perpetrated by insiders, who have access to data before it is processed.
The other answers are incorrect because :
IP Spoofing is not correct as the questions asks about the crime associated with the insiders. Spoofing is generally accomplished from the outside.
Password sniffing is also not the BEST answer as it requires a lot of technical knowledge in understanding the encryption and decryption process.
Denial of service (DOS) is also incorrect as most Denial of service attacks occur over the internet.
Reference : Shon Harris , AIO v3 , Chapter-10 : Law , Investigation & Ethics , Page : 758-760.