F-Secure detects ransomware using a variety of signature and generic detections. Once detected, the F-Secure security product will automatically disinfect the suspect file by either deleting it or renaming it.
If the ransomware uses encryption to take files or an entire system hostage, the encryption may be sufficient to make it very difficult to decrypt the files without the necessary decryption key.
In such circumstances, the recommended course of action is to report the crime to the relevant authorities and restore the affected data from a backup.
Trojan:W32/Nymaim has been found to be delivered via exploit kits, or in files (typically using filenames related to popular keyword searches) that are downloaded from various malicious websites.
If Nymaim is launched on a device, it will attempt to either lock the screen or download additional malware. If the user is located in a country in Europe or North America, the malware will download a customized lockscreen for that particular country; the lockscreen will display the ransom demand. If the user is in a country for which no customized lockscreen is available, Nymain will download a second-stage component which can be used at a later time to download additional malware.