If it's kept online, it can be hacked. If you want to protect YOUR files, you need a plan. Try a few, or all of the things listed below, and your chances of being hacked will be minimal.
Create strong passwords. (Don't write them down online, unless you are sure it is in a secure place.)
Keep your antivirus up to date.
Try to avoid dodgy sites, that look laid out badly- with excessive adds and/or download now buttons.
Don't click on links in your email if it is not from a trusted person. (People re-create bank login pages etc.)
Only log on to legitimate wifi networks, some may be set up just to get information. (Usually a device will tell you if the wifi looks dodgy.)
Don't download apps that you can see have access to things they don't need to. (For examples, a drawing app shouldn't need access to your contact list or network info.)
Don't save your password's on a computer that can be accessed by other people, or stolen and unlocked.
To protect yourself it is better to know more about cyber safety. Watch a few, or all of the videos below to increase your knowledge!