Monero (XMR) is a secure, untraceable, anonymous cryptocurrency based on the application layer protocol called CryptoNote. The digital currency was launched on April 18, 2014, emerging from the Bytecoin network hard fork (Bytecoin was the first anonymous cryptocurrency ever).
Unlike the majority of digital currencies, Monero transactions can't be traced, and no one can observe your balance since the network is running on the CryptoNote protocol. It ensures user's anonymity by ring signatures hiding the sender and a system of stealth addresses providing the receiver with complete anonymity.
A ring signature is a type of digital signature. The message signed with it is endorsed by someone in a particular group of people, but it's computationally infeasible to determine which of the group members' keys was used to produce the signature. Stealth addresses are signed by two private keys—the spend key for sending payments and the view key for displaying incoming transactions. You can decide who can see your Monero balance by sharing your view key.
This technology was approved by Bitcoin Core developer, Greg Maxwell: "Monero is private in ways that other systems that claim to be private can't match. It is an interesting project which is far more valuable than almost all other altcoins (and Monero is one of the only if not the only altcoin that I don't think is massively overpriced relative to Bitcoin)."
The full privacy of the cryptocurrency well explains its popularity on the black market—remember Libertas, the first Monero only darknet market? Besides, this September, the U.S. Department of Homeland Security reported that illegal Bitcoin transactions have decreased from half of all transactions to less than 20% of all transactions while Monero saw an increase in such operations. No precise figure was given, though.
Currently, the project is led by the team of seven developers, with only two of them publicly admitting it—Riccardo Spagni and Francisco Cabañas. Five others are working under a nickname.
Among cryptocurrency's disadvantages are a large blockchain size—which is eight times the size of the Bitcoin blockchain—scalability issue, and infinite inflation.
Monero enables its users to make anonymous payments and confront any attempts at regulation by the government. Given that anonymity is highly valued in today's crypto market, it's no surprise that Monero with its $4.7 billion market cap is among the ten largest digital currencies, making it to the ninth place on the list. This month, the price has increased by 2.5 times and is now hovering around $300 levels.