Answer:
code injection
Explanation:
Validating the data in a database prevents someone from sneaking code to run without permission, aka code injection.
Phishing - this is disguising as a reputable company/person and trying to steal info (passwords, credit card numbers)
Botnet - this is a network of computers (most likely in the network because of a virus) that are used as a group for malicious purposes (like spam)
Denial-of-service - this is an attack which aims to deny users from accessing the content they want. a common example of this is flooding a server with spam requests, rendering it overloaded and unable to handle any user requests
