* 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 TROJAN REMOVER can identify and eradicate all types of backdoor programs and trojans.* Educate your users not to install applications downloaded from the internet and e-mail attachments.
