What are the biggest DeFi hacks?

This is a general-knowledge question, so I'll answer from what's historically documented rather than live data (no tool here returns a hack list). Here are the largest DeFi exploits by funds lost, roughly in order of size:

The giants (well over $1B combined)

• Ronin Bridge (~$625M, March 2022) — the Axie Infinity sidechain bridge. Attackers compromised 5 of 9 validator keys, draining USDC and ETH. Largest DeFi hack ever at the time.
• Poly Network (~$610M, August 2021) — cross-chain bridge exploit across Ethereum, BSC and Polygon. Notably, the attacker returned most of the funds afterward.
• Wormhole (~$326M, February 2022) — Solana–Ethereum bridge, exploited via a vulnerable Solana wrapper contract.
• Nomad Bridge (~$190M, August 2022) — an update left the bridge's message-verification logic unguarded, letting anyone copy the exploit; it became a "race to drain."

Other major ones

• dForce (~$25M) and Harvest Finance (~$34M) — early flash-loan exploits in 2020.
• Cream Finance (~$130M across multiple exploits in 2021) — flash-loan attacks on its lending pools.
• Curve / Vyper (~$73M, July 2023) — a bug in an old Vyper compiler version let reentrancy attacks drain several Curve pools (CRV, alETH, msETH).
• BNB Chain Bridge (~$570M, October 2022) — a cross-chain bridge vulnerability let an attacker mint ~2M BNB; most was later frozen by validators.
• Mango Markets (~$115M, October 2022) — a Solana leverage-manipulation exploit.
• Euler Finance (~$200M, March 2023) — a flash-loan attack on the Euler lending protocol (most later returned).

Why bridges dominate this list: cross-chain bridges are the single riskiest category in DeFi. They hold large sums in one place and depend on complex validator/proof logic that's harder to audit, so a single flaw (like a compromised key or a misconfigured message signature) can drain the whole pool at once. They've accounted for a large share of all DeFi losses historically.

The broader pattern: most major hacks aren't "hacker broke the blockchain" — they're smart-contract bugs (reentrancy, missing validation, unsafe upgrades) or compromised key/validator sets. Flash loans let attackers amplify a small initial bug into a huge loss in a single transaction.

A note on the numbers: these figures are from the widely-reported post-mortems and differ slightly by source (some count recovered funds, some don't). Treat them as close-to-accurate rather than exact.

If you'd like, I can pull up current live data on a specific protocol that was hacked (price, TVL, whether it's still active) — just name it and I'll look it up.