Hackers more than doubled their cryptocurrency spoils in the first half of 2024 compared with a year ago, a report from blockchain research firm TRM Labs showed.

The report said $1.38 billion worth of crypto was looted between Jan. 1 and June 24, more than twice as much as the $657 million stolen in the same period a year ago. Like last year, a handful of large attacks drove the increase in plundered crypto, with the top five hacks accounting for 70% of the amount stolen in the first half of this year.

Top attack vectors in 2024 include private key and seed phrase – a sequence of random words that stores the information needed to access or recover a crypto wallet – compromises, said TRM Labs.

The largest heist so far this year swiped more than $300 million worth of bitcoin from Japanese crypto exchange DMM Bitcoin.

Hackers used stolen private keys or address poisoning – where attackers send a small amount of crypto from a wallet with a similar-looking address crafted to mimic yours or your recipient’s, with the intention to trick the victim into sending funds to the wrong wallet.

Crypto addresses are long, complex strings of characters that are difficult to memorize or manually enter without making mistakes.

TRM Labs said there have not been fundamental changes in the crypto ecosystem’s security that could have contributed to the increase in amount stolen. It said the number of attacks and attack vectors were not significantly different year over year.

But the firm noted that crypto prices have been higher on average in the first half of this year, which could have contributed to the higher value of stolen crypto.

Crypto companies have been frequent targets for hacks and cyberattacks.

Crypto exchange Mt. Gox filed for bankruptcy in 2014 after a series of hacks stole up to 950,000 bitcoin – worth more than $54 billion at today’s prices.

In November, about $115 million was stolen from HTX exchange and Heco Chain, two crypto platforms linked to high-profile entrepreneur Justin Sun.

Crypto firms can combat against hacks and exploits with a multi-layered defense strategy, including measures like regular security audits and robust encryption, said TRM Labs.

Educating employees and implementing a comprehensive incident response strategy can also help protect companies, it said.