How to Identify When a Trojan Virus Takes Control of the Keyboard

by Rebecca Bragg

Trojan---or Trojan horse---viruses come in many different disguises, but collectively they are among the most dangerous of all computer threats, capable of taking total control of your system without your knowledge. According to Microsoft, whose operating systems are a favorite target of many forms of malicious software, the most common vectors of transmission are email attachments, instant messaging programs, emails containing images, greeting cards and amusing audio/video files, also known as "glurge." Any message that tells you to forward it to all your friends is especially likely to be infectious, Microsoft warns. Trojans may also be picked up from downloads of infected sites, typically those that appear to be offering a free service.

Signs and Symptoms of Trojan Attack


Watch for slowdowns of keyboard function. Trojans put an added strain on your computer system's memory, Internet connection and bandwidth. If you notice an unusual lag between the time you press a key and the appearance of the letter on your screen, especially when typing into a search box, your computer may be infected.


Check the status of your antivirus protection. Computer hackers are experts who try to stay one step ahead of anti-malware programmers and sometimes succeed, meaning that updates can arrive after the damage has been done. Some Trojans evade detection and some can disable your antivirus software entirely. Run a diagnostic scan to see if your antivirus software is working.


Try entering sites offering anti-malware downloads. A Trojan's No. 1 priority is survival and to that end, it may be programmed to block your computer's access to any sites distributing---or even providing information about---software designed to wipe it out. If your access to such sites is continually blocked, it's a strong sign of trouble.


Beware of unusual pop-ups, error messages and icons. Flashing "alerts" claiming that your system is infected with Trojans and other malware may advise you of the urgent need to download a protective update immediately. Fake alarms, often disguised as messages from your operating system---especially if you use Windows---are called "Software Detection Killers," meant to destroy anything that might destroy the Trojan. An authentic warning that downloading this type of file may harm your computer should appear across the bottom of your screen. If so, click on "discard." Any new icons that suddenly appear on your desktop should also be considered suspect.


Treat Trojan infections as technical emergencies. Once these viruses have infected your system, all your data, including document files and email, may be accessible to the attackers. Every keystroke on your keyboard can be monitored, including passwords to bank accounts and confidential sites. If all your anti-malware protection has been disabled by the virus, you may need the services of a professional to scrub the infection out of your computer.

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