A Trojan horse is an unauthorized program contained within a legitimate program. This unauthorized program performs functions unknown (and probably unwanted) by the user.

• It is a legitimate program that has been altered by the placement of unauthorized code within it; this code performs functions unknown (and probably unwanted) by the user.
• Any program that appears to perform a desirable and necessary function but that (because of unauthorized code within it that is unknown to the user) performs functions unknown (and definitely unwanted) by the user.

Working of Trojans

 

• Attacker gets access to the trojaned system as the system goes online
• By way of the access provided by the trojan attacker can stage attacks of different types.

Various Trojan Types

• Remote Access Trojans
• Password Sending Trojans
• Keyloggers
• Destructive
• Denial Of Service (DoS) Attack Trojans
• Proxy/Wingate Trojans
• FTP Trojans
• Software Detection Killers

Modes of Transmission

• Attachments
• Physical Access
• Browser And E-mail Software Bugs
• NetBIOS (File Sharing)
• Fake Programs
• Un-trusted Sites And Freeware Software

Backdoor Countermeasures

• Most commercial ant-virus products can automatically scan and detect backdoor programs before they can cause damage (Eg. before accessing a floppy, running exe or downloading mail)
• An inexpensive tool called Cleaner (http://www.moosoft.com/cleanet.html) can identify and eradicate 1000 types of backdoor programs and trojans.
• Educate your users not to install applications downloaded from the internet and e-mail attachments.

Visitors who read this post, also read:

1. Common Terminologies used in Internet Security

2. Denial Of Service Attack