A user downloaded what appears to be genuine software.

The scenario described is characteristic of a Trojan. A Trojan is a type of malware that disguises itself as legitimate software but performs malicious actions once installed. Unlike viruses, which can replicate themselves, or worms, which can spread across networks on their own, Trojans rely on the guise of legitimacy to trick users into initiating their execution. In this case, the user believed they were downloading and installing genuine software, but the reality was that the application contained a Trojan. The malicious code executed upon installation provided unauthorized remote access to the user's computer, which could be used by an attacker to control the system, steal data, install additional malware, or carry out other malicious activities.

Trojans can come in many forms and can be used to achieve a wide range of malicious objectives, making them a versatile and dangerous type of cyber threat. The deceptive nature of Trojans, exploiting the trust users have in what appears to be legitimate software, is what makes them particularly effective and widespread.