Crypto exchange Binance is investigating what could be the biggest crypto hack in history as users saw upwards of $5.7 billion in funds drained from wallets Thursday afternoon.

Why it matters: The suspected hack comes after a wave of high-profile cyberattacks and data breaches during so-called "Black October," when a series of hacks and AI-discovered bugs triggered fears of a global crisis.

Driving the news: Binance co-founder Yi He said on X that the crypto exchange had suspended deposits and withdrawals after a hack. "User funds are safe," she wrote. "Binance will cover all hacking losses."

  • Analysts and traders who follow the crypto markets closely estimate that $1.7 billion to $5.7 billion was taken during the suspected cyberattack.
  • "This is unprecedented," said Kevin March, a co-founder of JPEG Trading, a cryptocurrency trading firm that closely tracked the hack to monitor market conditions.

Zoom in: Platforms including Tether and Circle froze more than $1 billion in cryptocurrencies, according to Binance co-founder Changpeng "CZ" Zhao, who is no longer an executive at the exchange. Such a step that would limit the scope of customer losses.

  • A Binance spokesperson said the exchange's security teams are "reviewing all relevant information with urgency."

The big picture: If estimates hold up, the suspected Binance hack would be the biggest crypto attack in history.

  • In 2025, North Korea-linked hackers stole about $1.5 billion worth of crypto from the Bybit exchange.
  • The country has turned hacking and scams into an industrial-scale scourge, focusing on crypto heists and a widespread practice of tricking Western companies into hiring North Korean workers.

Between the lines: Crypto is a relatively common hacking target, but massive attacks can leave smaller exchanges vulnerable to collapse due to the potential for panicked withdrawals.

  • Binance's size makes it more insulated, March said. "If this happened to any other business in crypto other than Binance, it would've been catastrophic."
  • The exchange is capable of covering potential losses through its insurance and balance sheet, he said, although broad reverberations in crypto markets and prices remain possible.

The intrigue: Reports of a breach came just hours after Polymarket confirmed it was facing a cyberattack, prompting the decentralized predictions market operator to pause trading for an hour after an attacker made off with at least $2.7 million in user funds.

  • Researchers at Hudson Rock tied the Polymarket incident to a breach involving third-party website monitoring tool DebugBear, which said earlier Thursday it was responding to its own security incident.

What to watch: Binance has yet to confirm who may be behind the attack and the total value of the currencies suspected hackers made off with.

Editor's note: This story has been updated with a statement from Binance's co-founder.