The Ethereum protocol itself is about as safe as you can get.
There's a story about a Silicon Valley entrepreneur who paid a security firm $500,000 to try to crack Bitcoin. After six months, they came back and said they couldn't break it. This is the same for the system that Ethereum is built upon.
The mathematics that Ethereum, Bitcoin and all other cryptocurrencies are built on are secure. There are no backdoors to be able to make a fake transaction. That is one of the reason why Ethereum and all other blockchains are still around today.
