The GandCrab ransomware first appeared in January and has been updated rapidly during its short life. It is the leading ransomware threat. The McAfee Advanced Threat Research team has reverse engineered Versions 4.0 through 4.2 of the malware.
The first versions (1.0 and 1.1) of this malware had a bug that left the keys in memory because the author did not correctly use the flags in a crypto function. One antimalware company released a free decryption tool, posted on NoMoreRansom.org, with help of Romanian police and Europol.
The second version of GandCrab quickly appeared and improved the malware server’s security against future counterattacks. The first versions of the ransomware had a list of file extensions to encrypt, but the second and later versions have replaced this list with an exclusion list. All files except those on the list were encrypted.