I think that cryptocurrency is secure the same value that you are secured, because you are the weakest part in all security system. You can show your private keys and nobody else could not.
That's right! We as humans are the flaw inherent within any security system. You can have an extremely secure system, but if you as a person or individual don't take the necessary precautions, then you'll be doomed. Many people have been hacked because of many obvious reasons, such as revealing their balances and private keys, using online wallets, carelessness of updating or installing an antivirus software, and more.
If you want to avoid being hacked as much as possible, then try to never disclose your personal information, as well as your private keys and current coin balances. Also, make use of a hardware wallet or cold storage since they're extremely secure by design. If you do that, then you'll be able to make a hacker's life impossible since he/she would need to gain physical access to your cold storage wallet or hardware wallet, to be able to steal your funds. When downloading a wallet software such as Bitcoin Core, or even Geth (for Ethereum), you would need to verify the authenticity of such software with the provided hashes. If the original devs software's keys dont match the ones you get from verifying the software, then you'll know that it has been modified, making it unsafe against hackers.
Once you do all of this, then it's very unlikely that your cryptocurrency funds will get hacked or stolen. What is needed is proper education to people who're new into cryptocurrencies, for them to be able to avoid such undesired situations. In my case, I've been using Bitcoin and other cryptos for quite a long time and had never been hacked because I always follow the necessary security procedures. If you do as me, you'll be fine.
