Protect your address: Although your user identity behind your address remains anonymous, Bitcoin is the most public form of transaction with anyone on the network seeing your balances and log of transactions. This is one reason why you should change Bitcoin addresses with each transaction and safeguard your address. You can also use multiple wallets for different purposes so that your balance and transaction history remain private from those who send you money.
Bitcoin (BTC) is a consensus network that enables a new payment system and a completely digital currency. Powered by its users, it is a peer to peer payment network that requires no central authority to operate. On October 31st, 2008, an individual or group of individuals operating under the pseudonym "Satoshi Nakamoto" published the Bitcoin Whitepaper and described it as: "a purely peer-to-peer version of electronic cash would allow online payments to be sent directly from one party to another without going through a financial institution."
Developing digital identity standards is proving to be a highly complex process. Technical challenges aside, a universal online identity solution requires cooperation between private entities and government. Add to that the need to navigate legal systems in different countries and the problem becomes exponentially difficult. E-Commerce on the internet currently relies on the SSL certificate (the little green lock) for secure transactions on the web. Netki is a startup that aspires to create an SSL standard for the blockchain. Having recently announced a $3.5 million seed round, Netki expects a product launch in early 2017.

Imagine this for a second, a hacker attacks block 3 and tries to change the data. Because of the properties of hash functions, a slight change in data will change the hash drastically. This means that any slight changes made in block 3, will change the hash which is stored in block 2, now that in turn will change the data and the hash of block 2 which will result in changes in block 1 and so on and so forth. This will completely change the chain, which is impossible. This is exactly how blockchains attain immutability.

So, what does blockchain technology bring to the table that current payment networks don't? For starters, and as noted, it's decentralized. That's a fancy way of saying that there's no central hub where transaction data is stored. Instead, servers and hard drives all over the world hold bits and pieces of these blocks of data. This is done for two purposes. First, it ensures that no one party can gain control over a cryptocurrency and blockchain. Also, it keeps cybercriminals from being able to hold a digital currency "hostage" should they gain access to transaction data.
The U.S. Commodity Futures Trading Commission has issued four "Customer Advisories" for bitcoin and related investments.[14] A July 2018 warning emphasized that trading in any cryptocurrency is often speculative, and there is a risk of theft from hacking, and fraud.[165] A February 2018 advisory warned against investing into "IRS approved" virtual currency individual retirement accounts.[166] A December 2017 advisory warned that virtual currencies are risky because:
Proof of work does not make attacks by hackers impossible, but it does make them somewhat useless. If a hacker wanted to coordinate an attack on the blockchain, they would need to solve complex computational math problems at 1 in 5.8 trillion odds just like everyone else. The cost of organizing such an attack would almost certainly outweigh the benefits.
In 2014, prices started at $770 and fell to $314 for the year.[32] In February 2014 the Mt. Gox exchange, the largest bitcoin exchange at the time, said that 850,000 bitcoins had been stolen from its customers, amounting to almost $500 million. Bitcoin's price fell by almost half, from $867 to $439 (a 49% drop). Prices remained low until late 2016.[citation needed]