Data from Defi Llama shows that cryptocurrency investors lost $664 million to hacks in the first half of this year, up more than 50 percent from the same period last year. Most of these losses come from phishing attacks and private key leaks. According to Omer Sadika, co-founder and CEO of blockchain security firm dWallet Labs, the proliferation of open-source hacking tools has lowered the barrier to entry for amateur hackers, increasing the number and frequency of attacks.