It’s clear from our research that the quality of the WannaCry code is poor and the developers made many mistakes, enabling many of those infected to recover encrypted data.  The way the attackers handled ransom payments limited their ability to capitalise on the spread of the worm.  Multiple attempts were made to track transactions to the bitcoin wallets used by the attackers.  Although estimates of how much money the attackers made vary, they run into tens of thousands, rather than hundreds .