Here are the results from one study-
Test machine:
2 Core, 2.9Ghz Intel i5 Windows VM with 4GB of RAM and an SSD.
Standard install.
1,000 word documents on the computer – approximately 70MB total size.
Time taken by different Ransomware to encrypt the disk completely:
Chimera: 18 seconds
Petya: 27 seconds
TeslaCrypt 4.0: 28 seconds
CTB-Locker: 45 seconds
TeslaCrypt 3.0: 45 seconds
Virlock: 3 minutes 21 seconds
CryptoWall: 16 minutes
It is definitely faster than we think!
You can read more here:
https://blog.barkly.com/how-fast-does-ransomware-encrypt-files