Discovered in 2013, the Nymaim Trojan is a malware that is most notorious for its functionality as ransomware. Once installed, the Nymaim ransomware blocks all access to the victim's computer, displaying a full screen message declaring that the victim's computer was blocked and that they face years of jail time and thousands of Euros in fines unless they pay a supposed police 'fine' through an online payment service.

This message will usually be tailored to the infected computer's geographical location, written in the victim's language and claiming to have been sent by a local police agency. Nymaim has been reported in cases of money extortion from people, hospitals, and even the police. Nymaim at its core is a downloader Trojan, and therefore also functions as a downloader for other malwares, such as the Ursnif banking Trojan.