Theoretically, a person can not hack crypto if it is in a wallet. It involves over-selling attacks. If you lose money then it is stealing, because your computer security and your wallet is not good enough. Bitcoin itself is almost impossible to hack as the blockchain technology that forms the basis of the currency is constantly under review by other Bitcoin users. This means that it is no more at risk than other payment methods just like traditional credit cards. However, just because Bitcoin itself isnt hackable does not mean it is completely safe to use. You have to look at the actual process of trading Bitcoin to find the vulnerabilities.
It is actually depend on the "thing" that people want to hack. Is it the blockchain ? Is it the market ? Is it the wallet account ? Is it the trading sites ? Is it the cloud mining sites, or something else. That is because, hackers can hack website and some other things. But there is something that hackers cannot touch and you guys have to know that. If we talk about the web based wallet on the browser. I think it is pretty save. As long as you make some complicated password that is random and do not contain date and someone's name. To be more safe, you have to change your password all the time, for like once a month, or once a week.