These events can occur in cryptocurrencies when they are compromised by malicious actors. Most commonly, the thief sends multiple packets associated with a transaction to the currency network, but then reverses the transaction with the intention of making it appear as if it never happened.

For example, suppose wallet A only has a balance of 1 BTC and wants to send 1 BTC to wallet B and wallet C simultaneously. Before the transaction is confirmed, this is possible, but during the confirmation process, miners will time-stamp the first transaction so that the second transaction is considered a double spend and will be canceled. Double-spending was one of the main concerns associated with cryptocurrencies when they first emerged.