iCloud got hacked

To keep your account secure, see the following Apple articles:

Manage and use your Apple ID

Manage and use your Apple ID – Apple Support (UK)

Recognize and avoid phishing messages, phony support calls, and other scams

Recognize and avoid phishing messages, phony support calls, and other scams - Apple Support

If you think your Apple ID has been compromised

If you think your Apple ID has been compromised - Apple Support

Create a strong password for your Apple ID, It is best if your password consists of eight or more characters and include upper and lowercase letters, and at least one number. You can also add extra characters and punctuation marks to make your password even stronger. 

Never provide your password, passcode, security questions, verification codes, recovery key or any other account security details to anyone else. Apple will never ask you for this information.

See also the following Apple articles:

About the 'Trust This Computer' alert on your iPhone, iPad, or iPod touch

About the 'Trust This Computer' alert on your iPhone, iPad, or iPod touch - Apple Support

Authorize or deauthorize your computer for iTunes Store purchases

Authorize or deauthorize your computer for iTunes Store purchases - Apple Support 

Get a verification code and sign in with two-factor authentication

Get a verification code and sign in with two-factor authentication - Apple Support

why do you think your iCloud account was hacked?

You may need to increase security, use an Apple ID, 2 factor verification, and so on.