What is Ransomware?
Ransomware is a type of malicious software that carries out the cryptoviral extortion attack from cryptovirology that blocks access to data until a ransom is paid and displays a message requesting payment to unlock it. Simple ransomware may lock the system in a way which is not difficult for a knowledgeable person to reverse. More advanced malware encrypts the victim's files, making them inaccessible, and demands a ransom payment to decrypt them.[1] The ransomware may also encrypt the computer's Master File Table (MFT)[2][3] or the entire hard drive.[4] Thus, ransomware is a denial-of-access attack that prevents computer users from accessing files[5] since it is intractable to decrypt the files without the decryption key. Ransomware attacks are typically carried out using a Trojan that has a payload disguised as a legitimate file.
While initially popular in Russia, the use of ransomware scams has grown internationally;[6][7][8] in June 2013, security software vendor McAfee released data showing that it had collected over 250,000 unique samples of ransomware in the first quarter of 2013, more than double the number it had obtained in the first quarter of 2012.[9] Wide-ranging attacks involving encryption-based ransomware began to increase through Trojans such as CryptoLocker, which had procured an estimated US$3 million before it was taken down by authorities,[10] and CryptoWall, which was estimated by the US Federal Bureau of Investigation (FBI) to have accrued over $18m by June 2015.[11]
