An attacker sends a large number of SYN packets, but does not send any ACK messages back. The connection stays open and uses up the source's resources. What is this attack called?

A DNS cache poisoning attack

A ping flood

A half$-$open attack

A zero day exploit

Which of the following measures can prevent injection attacks? Select all that apply.

Data sanitization

Input validation

Log analysis systems

Flood guards

What is a tool that protects passwords by checking whether the input is coming from a machine or a human?

Antimalware software

A firewall

A CAPTCHA

A key logger