A Trojan is a malicious computer program or malware. Trojans are sometimes called viruses, but they are not the same thing because viruses can execute and replicate themselves, while Trojans must be executed by a user. Trojans are hidden in links or programs but can easily removed by an antivirus program.
Never open junk e-mails from unknown sources. Such e-mails usually contain links, programs, attachments that will install a Trojan.
Don't download and install programs from a website, unless you fully trust it. Some websites deceive their users by claiming that their software will be free of cost and perform virus scans, while the truth is that installing such programs leads to infection of your computer with viruses and Trojans.
Install firewall software on your computer. Firewalls block suspicious connections and links, effectively preventing your computer from Trojans and other malicious programs. Windows XP, Service Pack 2 or later, Windows Vista and Windows 7 are equipped with Windows Firewall. Click "Start", "Control Panel", then "Security Center". Click on "Windows Firewall". Click "On" if it is off, and finally click "Apply" to confirm the changes.
Keep your antivirus software fully updated, especially when you are connected to iIternet. An antivirus scan will detect malicious programs like Trojans and viruses. An antivirus program will prevent such programs from infecting your computer and will help remove malicious software. Top Ten Review has a comprehensive list of notable antivirus software. Check the Resources section for a link to this list.