Ransomware is a type of malware that locks or blocks an individual computer or devices and threatens them to leak the data if the ransom is not paid. Most simple ransomware is to just lock the system which is not difficult to reverse if the victim is knowledgeable. More advance malware uses techniques called cryotiyiral extortion. In this type, what the attacker do is that he encrypts the victim’s file and ask ransom for decrypting it. Since without the decrypting key it is not possible to recover the files, it is properly implemented. The ransom is asked in Bitcoin or some digital currencies as the digital currency is difficult to trace back. Today, the attack I spread over 50 countries countless computers. It is not only limited to desktop or laptops mobile phones and smart watch are also targeted.This malware is infected by the attacker on the victim’s system via a malicious email or website. Or if they have already infected with the backdoor from which they have entered.This attack is carried out by tricking the victim making him opening or downloading a malicious file that the user thinks as legitimate file. “Wannacry worm” is a type of malware that travels automatically without the user interaction between computers.Some examples are:• Reveton• CryptoLocker• CryptoLocker.F and TorrentLocker• CryptoWall• Fusob• WannaCry• Petya• Bad RabbitHow ransomware worksAttackers uses many techniques to get the ransom from the victim• A pop-up message is received or an email claiming a sum of money if not paid will lock the system.• To pay fine for using some illegal or unlicensed software or content and the victims are given instructions to pay the fine.• The attacker encrypts the devices and asks money to decrypt the product and promises to help them to prevent from future attacks• Threats the victims to destroy the data or leak the sensitive data onlineRansomware preventionRegular backup of devices and regular updating of software is advised from the experts to prevent against ransomware attacks. An individual should be careful before opening the attachments or the links in the emails received from the strangers. Victim should try as much possible to avoid paying ransoms.