Trojan Horse

Harmful Trojan Horse

A Trojan Horse is a computer program that releases a malicious, harmful code hidden inside a seemingly harmless programming or data, so it can get control of your computer and do damage, such as to the file allocation table on your hard disk. [1]

Useful Trojan Horse

In one case, a Trojan Horse was a program used to find and destroy computer viruses, however, in most cases this true and the Trojan Horse itself is part of the virus. [2]

Recovering from a Trojan Horse Attack

If your computer has been attacked by a Trojan Horse follow these steps immediately:

    1. Call IT Support if you have it: Notify them of the situation[3]
    2. Disconnect from the internet: In some cases intruders who sent the Trojan Horse may have access to personal information stored on your computer; if you disconnect your computer from the internet, it stops this activity.[4]
    3. Back up any important files: Copy or transfer important files onto a separate storage item (ie: CD, DVD, or flash drive); however it is important to note that these files should not be trusted--they may have become infected, so always scan them with an Anti-Virus program before reopening them on a different computer.[5]
    4. Scan your machine: Since your computer and/or operating system may be infected with a malicious program, it is safest to scan the machine from a live CD (or “rescue” CD) rather than a previously installed Anti-Virus program. Many Anti-Virus products provide this functionality. Another alternative is to use a web-based virus removal service, which some Anti-Virus software vendors offer. Another option is to use Microsoft’s web-based PC Protection Scan. The next best action is to install an Anti-Virus program from an uncontaminated source such as a CD-ROM. If you don’t have one, there are many to choose from, but all of them should provide the tools you need. After you install the software, complete a scan of your machine. The initial scan will hopefully identify the malicious program(s). Ideally, the Anti-Virus program will even offer to remove the malicious files from your computer; follow the advice or instructions you are given. [6]
    5. Reinstall your operating system: If the previous step failed to clean your computer, the most effective option is to wipe or format the hard drive and reinstall the operating system. Although this corrective action will also result in the loss of all your programs and files, it is the only way to ensure your computer is free from backdoors and intruder modifications. Before conducting the reinstall, make a note of all your programs and settings so that you can return your computer to its original condition. It is also vital that you also reinstall your Anti-Virus software and apply any patches that may be available.[7]
    6. Restore your Files: If you have backed-up your files, scan them with an Ant-Virus before restoring them into your computer.[8]