An attacker can control the network of a client in several ways. First of all, an attacker can relay blocks that he creates putting the user on a separate network through which he can access the required information. Secondly, an attacker can filter out the information required for stealing Bitcoins by executing a double-spending attack. Setting up the user to a separate network and creating a double-spending attack can help the attacker to watch transmissions going on, under the user’s ISP. The most important security issue is that all Bitcoin transactions are stored in a network, permanently and publicly. This means that anyone can see transactions and balance however name and identity are unavailable. If people with bad motives try to capture information and users keep using the same Bitcoin address, there is a high probability of theft. Apart from these issues, there is another major concern that might affect the use of Bitcoin in the future. It is known that Bitcoin uses SHA-256 and ECDSA algorithms for cryptography (Ransom, 2002, p.26). These algorithms are considered strong but it might be broken in the future. Hence stronger algorithms could be required to secure the payment mode of bit cons.