Reviewed and updated: October 19, 2026.
A DeFi vampire attack is an incentive campaign intended to attract liquidity or users from an established protocol. Sushi's 2020 campaign is a useful historical example because it shows why copying open-source code, attracting deposits and retaining economic activity are three different achievements.
The mechanism behind the name
Sushi's official glossary describes its 2020 use of SUSHI incentives to attract liquidity from Uniswap. The legacy MasterChef contract provides more concrete evidence of the mechanism: users deposited liquidity-provider tokens, and a migrator interface could exchange Uniswap V2 pool shares for SushiSwap pool shares.
An LP token represents a position in a pool, subject to that pool's rules. Moving the underlying liquidity requires redeeming or migrating that position and creating a corresponding position elsewhere. Copying source code alone does not move anyone's assets or create an equivalent market with active traders.
A code fork is not automatically a blockchain split
A team can copy and modify an application repository and deploy new contracts on the same blockchain. That is different from a disagreement over blockchain consensus rules that produces separate chain histories. Describing every software fork as a hard fork that creates a new blockchain confuses application competition with network consensus.
For a reader comparing two exchanges, the relevant records are the deployed contract addresses, pool assets, permissions and liquidity. A familiar interface or shared code ancestry does not establish that the contracts have identical settings or that one version inherits every security property of another.
What the historical contract reveals
The MasterChef source includes an owner-set migrator and approval of LP tokens for migration. It checks that the replacement LP-token balance matches the amount migrated. These are inspectable implementation details, not proof that every possible migrator or later version is safe. The repository is a historical artifact and should not be treated as a recommendation to interact with old contracts.
For any modern campaign, map which party can change the destination or migration code, what users authorize and whether they can exit before a change. A token reward rate says little about these permissions.
Worked example: incentive income versus trading income
Consider a fictional $10,000 LP position over a defined period. It earns $40 in trading fees and 100 reward tokens. At a hypothetical reward-token price of $1, those two income components total $140. At $0.20 per reward token, they total $60. Neither figure is the position's total investment return: changes in the underlying assets, divergence from holding them, transaction costs and taxes are omitted.
The calculation shows why a displayed reward APR can change sharply without an increase or decrease in genuine trading demand. A subsidy may attract deposits temporarily. Sustainable fee income needs actual trading activity and a pool configuration that serves that activity. This is an analytical distinction, not a claim about Sushi's present revenue.
A worksheet for evaluating liquidity campaigns
| Measure | Useful question |
|---|---|
| Deposited assets | How much is present, valued at which prices and date? |
| Trading activity | Does volume persist when incentives decline? |
| Reward funding | Who supplies rewards, and how long can the schedule last? |
| Control | Who can alter contracts, emissions or migration permissions? |
| Exit | What remains after fees, slippage and position-value changes? |
Keep the chronology and the conclusion separate
Uniswap's dated announcement introduced UNI on September 16, 2020. That establishes an event in the same competitive period; timing alone does not establish every motive behind it. This account avoids an unsupported exact migration day or dollar total. The documented lesson is narrower and more durable: incentives can move capital, but deposited capital is not the same as lasting customer demand.
Sources and scope
- Sushi: DeFi glossary and the 2020 vampire attack
- SushiSwap: legacy MasterChef contract source
- SushiSwap: legacy repository context
- Uniswap: Introducing UNI, September 16, 2020
Continue reading: The development of decentralized exchanges · Reading DeFi incident evidence
Editorial update: Separated application forks from blockchain forks; explained LP migration permissions; removed unsupported dates and causal claims; added an incentive-versus-fee-income example.
Pause and explain
What changes when the fictional reward token falls from $1 to $0.20?
Compare your explanation
The 100 reward tokens fall in value from $100 to $20. With $40 of trading fees, the two income components become $60 instead of $140. Neither amount is total return, and the fee component does not itself prove lasting demand.
Deposits and rewards do not establish that every rule is sound. The next lesson follows a documented valuation failure.
All five lessons · Change your learning level
Learning sequence added October 20, 2026. The article’s factual review date is shown above.