jpg file and change the name of the file to jpg.exe so that whenever a user opens the file, his computer gets infected unknowingly.

A virus can affect the Master Boot Record or MBR of a computer also. And when that happens, it can survive even after the re-installation of Operating Systems.

Computer viruses can perform many harmful activities like corrupting hard disks, deleting files, and degrading the performance of a computer. It can also display unrelated messages on a computer screen and steal private data by logging keystrokes, spam contacts, etc.

What is a trojan horse?

The word Trojan is derived from the ancient Greek wooden horse that the Greeks used to invade Troy stealthily. Trojan programs generally trick a user by using social engineering techniques and get loaded and executed into the system (What is a social engineering attack and how to prevent it ?) stealthily. They often misrepresent themselves to appear useful or interesting to the user and persuade the user to install it (What is phishing and how to prevent it?).

Trojans can infect a computer when a user clicks on a suspicious link, opens an email attachment, or even installs software from untrusted sources. Sometimes, trojans even misrepresent themselves on unsafe websites as Anti-Virus software and when a user installs the rogue software, trojans infect the computer.

But unlike computer worms and computer viruses, trojans do not self-replicate themselves. Spyware (What is spyware and how to prevent it?) and ransomware (What is ransomware and how to prevent it ?) are usually types of trojans. Spyware infects a computer to steal sensitive private data or spy on the activities of the user. Ransomware encrypts useful data of victims and makes the system inaccessible to the user for the purpose of blackmailing or extorting money from the victim.

Trojans, when they infect a computer with elevated privileges, can do much harm. They can corrupt hard disks, corrupt data, crash a computer, format disks, infect the MBR or Master Boot Record of a computer, and they can even steal sensitive private data or encrypt user files to extort money.

You can get more information on trojans here: What are trojans and how to prevent them?

How to prevent computer worms, viruses, and trojans?

Computer worms, computer viruses, and trojans have similar prevention techniques.

• Do not click on suspicious links.
• Do not open suspicious email attachments or click on any link in an email sent by an unknown sender.
• Install software from trusted sources only.
• Keep your operating system, browser, and all other commonly used software updated with recent security patches. The more updated software is, the lesser its known security vulnerabilities.
• Install anti-malware programs from trusted sources only and keep them updated regularly.
• Do not pay a ransom if someone is trying to extort money by infecting your computer. Because paying the ransom does not guarantee that you will get back your data or you won’t get infected by the same ransomware again.
• Take regular backups of your data so that you can reinstall the system from the backup at any time in case malware like ransomware infects the system. You can get more information on how to take backup here: Some simple ways to backup your data.
• Use a different browser for opening banking websites and keep the browser updated regularly. You can get more information on how to increase the security and privacy of browsers here: A comprehensive guide to increasing the security and privacy of your browser.
• Do not visit unsafe websites. Use a Virtual Machine for browsing unsafe websites and destroy the VM once you are done.
• If you are tech-savvy, you can think of using a Virtual Machine or other containers to do all the browsing work. The advantage of this is that if the container gets infected, you can always revert it to some previous snapshot or destroy it completely and create a new one.
• Configure the proper firewall on your system (What is a firewall and how does it work ?). It is better to prevent unnecessary applications from accessing the Internet. Close unused ports. And it is always good to prevent two systems in a local network from interacting with each other if it is not required. If malware infects a system in a local network, it should not infect other devices in the same local network so easily.

I hope this helps. Interested readers who want to know more about how different malware and cyberattacks work and how we can prevent them may want to refer to the book “A Guide To Cyber Security.”

Security Fundamentals Practice Tests

The Security Fundamentals Practice Tests test one’s fundamental knowledge of cyber security. The practice tests are good for those who are preparing for various certification exams like the CCNA, CCNP, or CompTIA. They are also good for students and IT/security professionals who want to improve their understanding of cybersecurity.