What is the function of computer backdoor

What is a computer backdoor program and the reasons why it occurs

Speaking of the word "backdoor", I believe everyone has heard of it, dictionary Interpretation: The door at the back of the room that can be freely entered and exited, the entrance in the opposite direction to the main entry route. So what is a "computer backdoor"? (Recommended learning: web front-end video tutorial)

Early computer hackers, after successfully gaining control of the remote system, hoped to have a technology that would allow them to access the remote system again at any time. Enter the remote system, and the backdoor program appears.

The explanation of "backdoor program" on Baidu Encyclopedia is as follows: Backdoor program generally refers to those program methods that bypass security controls and gain access to a program or system. During the development phase of software, programmers often create backdoor programs within the software so that flaws in the program design can be modified.

However, if these backdoors are known to others, or the backdoor programs are not removed before releasing the software, then it becomes a security risk and can be easily exploited by hackers as vulnerabilities.

In fact, we can summarize it in a very simple sentence: The backdoor is a way to stay in the computer system for a special person to control the computer system in a special way! !

Classification of backdoors

1. Web page backdoors

This type of backdoor program is generally a normal web program on the server services to construct their own connection methods, such as the very popular ASP, cgi script backdoors, etc.

Typical backdoor programs: Top of the Ocean, Pretty in Pink Personal Edition, and later derived many versions of this type of web backdoor, written in the language asp , aspx, jsp, php all have a wide variety.

2. Thread insertion backdoor

Use a service or thread of the system itself to insert the backdoor program into it. This kind of backdoor has no process when running. Network operations are broadcast to the processes of other applications.

Typical backdoor program: represents BITS, xdoor (the first process insertion backdoor) is also a process insertion backdoor.

3. Extended backdoor

The so-called extended backdoor, understood in a common sense, can be seen as integrating a lot of functions into the backdoor, making the backdoor itself It can realize many functions and facilitate direct control of broilers or servers. This type of backdoor is very popular among beginners. It usually integrates file upload/download, system user detection, HTTP access, terminal installation, port opening, start/stop service, etc. The function itself is a small toolkit with powerful functions.

Typical backdoor program: Wineggdroup shell

4.C/S backdoor

This backdoor uses ICMP channels for communication, so no ports are opened. It just uses the ICMP packet of the system itself for control. After it is installed as a system service, it runs automatically when it is turned on. It can penetrate many firewalls. It is obvious that its biggest feature is: it does not open any ports ~ it is only controlled by ICMP! It is the same as any of the above. Compared with other backdoor programs, its control method is very special. Even port 80 does not need to be opened. I have to admire the unique thinking angle and vision of service program compilation in this regard.

Typical backdoor program: ICMP Door

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