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    The difference between viruses, worms and trojans

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    Pau Monfort

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    In this article, we'll introduce you to some of the ways hackers can use Trojans, viruses, and worms to compromise a computer system. We will also look at the countermeasures that can be used to protect yourself from such activities.

    Some of the abilities of hackers are computer programming and networking skills. They often use these skills to gain access to systems.

    The goal of targeting an organization is to steal sensitive data, disrupt business operations, or physically damage computer-controlled equipment. Trojans, viruses and worms can be used to achieve the above objectives.

    The difference between viruses, worms and trojans

    • What is a Trojan?
    • What is a worm?
    • What is a virus?
    • Trojans, viruses and worms, countermeasures

    Interesting article: How to recover files deleted by viruses, easy guide

    What is a trojan?

    A Trojan horse (trojan) is a program that allows the hacker to control the user's computer from a remote location

    The program is usually disguised as something that is useful to the user. Once the user has installed the program, he has the ability to install malicious payloads, create backdoors, install other unwanted applications which can be used to compromise the user's computer, etc.

    The following list shows some of the activities the attacker can perform using a Trojan horse.

    • Use the user's computer as part of the botnet when performing distributed denial-of-service attacks.
    • Damaging the user's computer (crash, blue screen of death, etc.)
    • Stealing sensitive data such as stored passwords, credit card information, etc.
    • Editing files on the user's computer
    • Electronic money theft through the execution of unauthorized money transfer transactions
    • Record all keys that a user presses on the keyboard and sends the data to the attacker. This method is used to collect user IDs, passwords and other sensitive data.
    • Viewing the screenshot of users
    • Download of browsing history data

    What is a worm?

    A worm is a malicious computer program that usually replicates itself over a computer network. An attacker can use a worm to perform the following activities;

    • Install the backdoors on the victim's computers. The created backdoor can be used to create zombie computers which are used to send spam emails, perform distributed denial-of-service attacks, etc. Backdoors can also be exploited by other malware.
    • Worms can too slow down the net by consuming the width di band during replication.
    • Install the malicious payload code contained in the worm.

    What is a virus?

    A virus is a computer program that attaches itself to legitimate programs and files without the user's consent. Viruses can consume computer resources such as memory and CPU time. Attacked programs and files are said to be "infected". Computer viruses can be used for;

    • Access private data such as user ID and password
    • Show annoying messages to the user
    • Corrupted data on your computer
    • Record user keystrokes

    Computer viruses are known to employ social engineering techniques. These techniques involve tricking users into opening files that appear to be normal files such as Word or Excel documents. Once the file is opened, the computer virus code runs and does what it is intended to do.

    Viruses, worms and trojan viruses, countermeasures

    To protect itself from such attacks, an organization can use the following methods.

    • A policy that prohibits users from downloading unnecessary files from the Internet such as spam email attachments, games, programs that claim to speed up downloads, etc.
    • Antivirus software must be installed on all users' computers. Antivirus software must be updated frequently and scans must be performed at specified time intervals.
    • Scan external storage devices on an isolated machine, especially those that come from outside the organization.
    • Regular backups of critical data should be performed and preferably stored on read-only media such as CDs and DVDs.
    • Worms exploit vulnerabilities in operating systems. Downloading operating system updates can help reduce worm infection and replication.
    • Worms can also be avoided by scanning all email attachments before downloading them.

    You may be interested in: Best antivirus Windows 10, effective and free

    How to defend against Trojans, viruses and worms

    Trojan virus

    • Malicious program used to control a victim's computer from a remote location. Stealing sensitive data, spying on the victim's computer, etc.


    • Self-replicating program that attaches itself to other programs and files. Stop normal computer use, damage user data, etc.


    Illegitimate programs that usually replicate themselves on the network. Install backdoors on victim's computer, slow down user's network, etc.

    Read also: The nine best antivirus online


    Use of antivirus software, update patches for operating systems, security policies on Internet use and external storage media, etc.

    Further Reading:

    • What is a trojan virus?
    • The best alternatives to Avast Antivirus
    • What is dllhost.exe file? How do I remove it from Windows 10?
    • 4 ways to remove Trojan horse malware from Windows 10
    • Virus vs. malware: what's the difference?
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