What is Trojan Horse
The term Trojan horse is applied to malware that masquerades as a legitimate program but is in reality a malicious application. It may simply pretend to be a useful program or it may actually contain a useful function as a cover for a destructive program at the core. Screen savers are often used as a carrier. Trojan horses do not replicate themselves as do viruses and worms. However, a Trojan horse can be part of the payload of a worm and can be spread to many machines as part of a worm infestation. Many Trojan horse are sent out as email attachments.
One favorite use of Trojan horse is to allow a malicious hacker ( more properly called a "cracker") to use systems of unsuspecting owners for attacking other machines or as zombies (explained below). Another use is for relaying spam or pornography. Yet another use is to steal account passwords and then relay them back to someone for fraudulent use. Trojans can also be destructive and wipe out files or create other damage. Recently, phishing scams have been making use of Trojans.
What is a Zombie Computer
A zombie computer (abbreviated zombie) is a computer connected to the Internet that has a hidden software program or "backdoor". This backdoor allows the computer to be remotely controlled by others. Some uses for a zombie include conducting distributed denial of service attacks(also known ad DOS attacks) or sending spam in such a way that attacker's true identity is not revealed!
Solutions / Remedies to Trojan Horses
Most Trojans are recognized by the major anti-virus programs. However, not all Trojans have characteristics that anti-virus programs do understand so additional software like spyware-removers is recommended. The spyware programs should be considered as well.
It is essential in the present conditions to have a firewall. The Internet is a two-way street. Unless your computer is properly protected, it is too easy for unwanted visitors or programs to gain access to your computer while you are online. A cracker can plant a Trojan or worm or do other harm. Good firewall software can make your computer invisible to all except the most determined cracker - the person who has got only one aim - to destroy your computer. Also most firewalls will warn you if programs on your computer try to connect to the Internet without telling you. That will help to warn you if you get an infection. However some Trojans may hide using essential services like your email client.
Windows XP has half a firewall built in. Unfortunately, it monitors only incoming traffic and therefore is of no help in warning about programs on your computer that call up Internet sites without telling you. Also, note that that you have to specifically enable it. (Service Pack 2 turns it on by default.). A more robust programs recommended instead. If you want to, you can go for one of the commercial suites that include a firewall together with a variety of other programs. However, there are several very good free programs.
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