Malware
ATANK
According to Lukas Stefanko, this is an open-source crypto-ransomware found on Github in 2018.
ATANK is a Android malware family.
Background
Lukas Stefanko identifies this as open-source crypto-ransomware that surfaced on Github in 2018. It can encrypt and decrypt files (AES, with a key of 32 random characters that is sent to the C&C), relies on email as its contact channel, and deletes all files after 24 hours or following a reboot.
Source: Malpedia (Fraunhofer FKIE).