The NSA attempted to track down Bitcoin users primarily, although it did show some interest in other cryptocurrencies as well, according to media reports, citing leaked documents from 2013 obtained by Snowden.
The surveillance did not stop at the users' activities carried out via the blockchain technology that supports cryptocurrency, but extended to their Internet activity, passwords and MAC addresses, a computer's unique identifiers.
The main focus of MONKEYROCKET data collection was terrorism, as it hoped to attract as well as track people who might be engaged in terrorist activities.
Snowden disclosed a number of US surveillance programs in 2013 and had to flee the United States, where he was facing charges of espionage and theft of government property. The former NSA contractor subsequently arrived to Moscow, where he was granted temporary asylum and has been residing ever since.