Hidden Tear is the first open-source ransomware trojan that targets computers running Microsoft Windows[1] The original sample was posted in August 2015 to GitHub.
[2] When Hidden Tear is activated, it encrypts certain types of files using a symmetric AES algorithm, then sends the symmetric key to the malware's control servers.
[3] However, as Utku Sen claimed "All my malware codes are backdoored on purpose", Hidden Tear has an encryption backdoor, thus allowing him to crack various samples.
[4]