Which of the following defines a rootkit? Question $18$ options: $1)$ It is the act of fraudulently using email to try to get the recipient to reveal personal data by sending legitimate$-$looking emails urging the recipient to take action to avoid a negative consequence or to receive a reward. $2)$ It is the unintended release of sensitive data by unauthorized individuals. $3)$ It is the abuse of email systems to send unsolicited email to large numbers of people. $4)$ It is a set of programs that enables its user to gain administrator$-$level access to a computer without the end user$$s consent or knowledge.