How does a backdoor works

[Daniel23]

Hi,
I need some detailed information on a backdoor virus. How does that works and what are the damaged caused by it. I manage a wide network. Recently we had found a Trojan virus in the network which entered via a email. To get more easy catch I want the complete technical working process of this type of virus. What does it do and how it enters a systems.

[Shen]

In the case of an application, the backdoor is often a bit of code for security procedure and thereby facilitate the testing or troubleshooting present in the final version of the program, the code allows that it is aware run the application without authorization or even break into the system. In the case of a computer, the backdoor is a small program installed automatically by a virus or manually by an attacker unknown to the user, it can take remote control system, or when an intrusion to return later without having to force it back to safety.

[Steve123]

In the software case a backdoor is a feature unknown to the legitimate user, which gives access to the secret software. In computer security, the backdoor can be considered a kind of Trojan horse. A backdoor can be made either by the software developer or by a third party, typically a computer hacker. A person familiar with the backdoor can be used to monitor the activities of the software, or gain control (for example, authentication bypass).

[Milton.J]

Depending on the extent of rights that provides operating system software contains the backdoor, control may extend to all operations of the computer. The widespread networking of computers makes backdoors much more useful than when physical access to the computer was the rule. The practical easily accessible and always open the software to efficiently conduct maintenance actions. The ability to surreptitiously disable the software if they disagree with his client.

[Spyrus]

The backdoor has the ability to monitor what the legitimate user and copy or destroy data with a value (passwords, private key to decrypt messages private banking information, trade secrets). It can also take control of a computer and can use it to carry out evil actions (including sending spam to phishing, computer viruses, denial of service).

[Snake08]

Backdoor can take control of a vast network of computers (botnet) that can be used to blackmail the distributed denial of service (DDoS), or resold to criminals. To install backdoors mass hackers use viruses. They will recline automatically and install a computer server on each infected computer. Then the attacker can connect to the Internet through a server. A backdoor can be inserted by way of Easter egg, compiler, or may take the form of a program like Back Orifice.