Even though it’s very safe to transact in Bitcoins, there can be a possibility of an attack on the transactions. Some of them are:

51% Attack

The 51% attack is based on the computational power required by a blockchain network. When a miner controls over 50% of the network’s mining power, they can manipulate a transaction in their favour. This is just an assumption as it’s almost impossible to have that level of computing power.

Fraudulent Activities

Some miners may indulge in fraudulent activities and try double-spending the bitcoins. The Finney attack is an example of this form of illegal activity. This depends on the vendors entitled to receive bitcoins. Sometimes, they may release services or goods before their payment is confirmed. In such cases, a miner may duplicate the transaction to pay themselves and get the actual one rejected by the network. To safeguard themselves, vendors must wait for 5-6 blocks to be mined before providing goods or services.  

Identity Theft

Public key cryptography is very reliable in maintaining the anonymity and security of a transaction and the parties involved. However, this relies on keeping the private key secure. If the security of the private key is compromised, the transaction may be manipulated.