Signs that you might have been hacked might include getting lots of “pop ups” from companies offering stuff you haven't even asked for - or your device noticeably starting to slow down.
So, what do you do first if you think you've been hacked? Tell a parent or carer, and then let your friends know so they can stop themselves being hacked too.
While there’s no foolproof way of keeping your online accounts safe, there's plenty you can do to limit the chance of someone breaking in. We’ve listed our top five tips below.