In the world of cybersecurity, understanding and recognizing the threat of a Trojan virus is vital. The key question, 'what is trojan virus', can be answered quite simply: it is a malicious code that hides in the guise of a legitimate program, tricking users into enabling its malicious activities.

Commonly disguised as a game, a video package, an email attachment, or a software installation package, once this menacing program is installed or executables are run, it gives the hacker complete control over your system. The hacker would then access your sensitive information or disrupt your device operation, giving rise to an army of cybersecurity issues.

The term ‘Trojan Virus’ stems from the Greek myth - the ‘Trojan Horse’. Just as the Greeks used a wooden horse to gain access into the fortified city of Troy, so does the Trojan virus trick its way into your device.

The Different Types of Trojan Viruses

Understanding 'what is trojan virus' is only the first step. Equally important is to know the different kinds of Trojan viruses lurking on the internet. Among the most common types are:

1. Backdoor Trojan: This creates a ‘backdoor’ in your system that provides hackers unauthorized access to your device, allowing them to send, receive, launch, and delete files.
2. Rootkit Trojan: This Trojan helps to conceal certain objects in your system from regular detection methods, thus aiding continued malicious activity.
3. Infostealer Trojan: True to its name, this type of Trojan is designed to steal information from your system.
4. Banker Trojan: These are designed to steal your bank account information, including passwords.
5. Distributed Denial of Service(DDoS) Trojan: This Trojan performs DDoS attacks, where a targeted system is flooded with traffic, causing a shutdown.

How to Recognize a Trojan Virus?

Understanding 'what is trojan virus' must also include the ability to recognize one. Look out for these symptoms:

1. Your device is operating slower than usual.
2. You notice an unusual loss of data.
3. Your device frequently crashes or freezes.
4. There are unfamiliar icons on your desktop.
5. Your antivirus or firewall is disabled without your knowledge.
6. There are strange pop-up advertisements even when you’re not online.

Preventing a Trojan Virus Infection

Since 'what is trojan virus' is no longer a mystery, let's learn how to prevent an infection with some easy steps:

1. Update Regularly: Keep your operating system, antivirus, and other software updated to patch any security vulnerabilities.
2. Install a Robust Antivirus Program: An antivirus program is your first line of defence against Trojan viruses.
3. Avoid Suspicious Emails: Do not open emails from unknown senders or download email attachments unless you’re certain it’s safe.
4. Browse Safely: Don’t click on suspicious links or pop-ups, and steer clear of websites that aren’t secure.
5. Use a Firewall: A firewall can block unauthorized access to your device.

Recovering from a Trojan Virus Infection

If you fall victim to a Trojan Virus, here are the steps towards recovery:

1. Run a full system scan using your antivirus software.
2. Delete all infected files.
3. Some Trojans are persistent and may need specialist removal tools, available on the websites of many antivirus providers or sometimes a fresh installation of the operating system is required.

In conclusion, understanding 'what is trojan virus', recognizing the symptoms, and knowing the measures for prevention and recovery can help safeguard your digital life. As cyber threats continue to evolve, keep yourself educated and aware to steer clear of these virtual troublemakers. Remember that contrary to the idea of 'out of sight, out of mind', these threats are incredibly real and can have tangible effects on your life if not countered effectively.