REvil ransomware overview
First, REvil collects information about the system and fingerprints it. Before starting the encryption process, it kills a list of processes according to its configuration.
Configuration data is stored in resources in encrypted form. The key is 32 bytes long and located before the encrypted data:
Once the processes are killed, it removes shadow copies, so they can't be used for data recovery.
It encrypts files using curve25519/Salsa20. The key is encrypted with curve25519/AES-256-CTR. REvil adds a custom extension to encrypted files, for example, .1qu4746az
.
It also changes the desktop wallpaper (dropped to the %Temp%
directory) and creates ransom notes in all directories with encrypted files.
To achieve persistence, REvil modifies the SOFTWARE\Microsoft\Windows\CurrentVersion\Run
registry key.
Abusing Administrative shares isn't the only technique...