“…similar exploits [to wannacrypt] were used not long ago by the NSA to get backdoor access to financial data within the SWIFT banking system. This was rather odd because through international agreements the NSA already had front door access to such data.
However, front door access can be tracked and traced and any illicit activity can be exposed.
Therefore, the NSA must have had something more nefarious in mind than simply looking for terrorist activity, such as testing the effectiveness of their own exploits for future use in attacks.”
http://www.zerohedge.com/news/2017-05-17/cyber-attacks-are-perfect-trigger-stock-market-crash