A hacker is a person or a robot controlled by a human which cracks someone’s password for an account e.g. social networking sites or email, then uses it. They can send messages from your account to other people, making them feel hurt, worried or even scared. To make sure your accounts are secure, make sure you have a back-up email for every account. Also, install or buy an anti-virus protection; hackers sometimes use viruses to hack computers, phones and even SIM card details.