It is a type of malware that typically gets hidden as an attachment in an email or the form of downloads.
Once downloaded, the malicious code gets executed to attack the computer systems. We call it a cyber attack.
Indications of a trojan acting on a device include usual activity such as computer settings unexpectedly.
The malicious file could be hidden in the banner, ads, pop-ups, or links on the website.
Hackers can use the malicious malware to produce similar malware in another system to get infected.