What happened
NeutrinoProtocol (NEUTRINO) is a BEP-20 token on BNB Smart Chain with an owner-controlled switch, _feeEnabled. When it is on, any transfer into the PancakeSwap pair created in the constructor takes a fee computed as mul(div(amount, 100), 100), which is the whole amount rounded down to a multiple of 100 base units, so the pair is credited almost nothing for the tokens a holder sells. The owner, the router and the token contract are exempt.
De.Fi's REKT database lists the token as an Exit Scam/Honeypot and says the contract owner could disable the transfer function, which restricted users in selling their tokens; the code has a sell-side fee switch rather than a function that disables transfers. De.Fi gives no loss figure.
How it happened
- The constructor creates the PancakeSwap pair for the token and stores it in
uniswapV2Pair;_feeEnabledstarts asfalse. - Only the owner can flip the switch:
function setFeeEnabled(bool feeEnabled) external { require(_owner == msg.sender); _feeEnabled = feeEnabled; }. The source does not show whether or when it was called. - In
_transfer, the sender is debited the full amount first:_balances[from] = sub(_balances[from], amount);. - When the switch is on and the recipient is the pair, the sender is not the router,
_owneror the token itself, the fee isuint256 fee = mul(div(amount, 100), 100);. For any amount of 100 base units or more this is almost the full amount (amount minus amount % 100). - The pair is credited only
sub(amount, fee), at most 99 base units, and the fee is subtracted from_totalSupplyrather than paid to anyone:_totalSupply = sub(_totalSupply, fee);. A holder selling through the pair therefore gives up their tokens and sends the pair nearly none. - Transfers where the sender is
_owneror the router, or where the recipient is not the pair, take theelsebranch with no fee. De.Fi's REKT database lists the token as Exit Scam/Honeypot; no transaction or loss amount was opened.
Protocol details
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