There is several ways to combat abuse of token bridges that convert between a coin and a wrapped token, or between two tokens.
- Make sure the destination address is not the NULL address or address that deployed the bridge contract
- Make sure the address has not sent another conversion request within last 24 hours
- Make sure the conversion amount is not very small
- Make sure the conversion amount is not too large
- Make sure the address that deployed the bridge contract has enough balance to cover the conversion transaction, if it's not paid by user
- Compare the destination address against static or dynamic blacklist and skip the conversion if the address does match
- Reject conversions if the conversion transaction would revert or throw an exception
- Reject conversion if the conversion amount is below minimum threshold
- Delay conversion if the destination address was used within last 24 hours.