yes, the bitcoin technology is very safe, and never it has been hack. But sometimes I can hear when I discuss of the bitcoin and other crypto currencies with my entourage "are you sure it's very safety", or "yesterday i've seen an article about the theft of a million euros in bitcoin" but it's the fault of the trading platforms which are less secure and not the blockchain itself. No one has ever hacked into the bitcoin system itself by modifying blocks for example. So it is safe for me.