Please be informed that Ransomware is one of a family of viruses that are used to extort money by encrypting the victim’s data and demanding a large sum of money for it to be decrypted. There are many variants of the Trojan but this has been the most widely publicized and the same rules apply when dealing with any other version. Crypto locker will most commonly be delivered via an email attachment. The mail may look as if it contains some important information, perhaps it appears to be a tax receipt or an invoice, maybe important information from a government source. Attached to the email will be what may appear to be a PDF document but which is actually an executable file; this isn’t always the case as the Trojan can be packed within a zip file or even be downloaded when a macro run from a spreadsheet is executed.
Once clicked on the Trojan will silently encrypt the victim’s data and only when the process has completed will it present the user with a ransom demand for the key required to decrypt the data. The criminals who are behind Ransom ware and similar attacks alter the code of their software and test it against antivirus products, this allows them a small window through which to attack, between the time that the Trojan is released and the time that Antivirus companies update their definitions. This is why the attackers use the most immediate method of reaching their victims, via email. AVG can remove the Trojan from your pc but the encrypted file cannot be unencrypted.