Trojan horse is a software, that is installed on a system and appears benign, but in actual it is the addition of malicious which unexpected modifications in config files and unusual activity even when the computer is idle are strong signs that a Trojan exists on a system. and other options are not correct that can be described as follows:
In option A, It is a malware that is also known as Trojan.
In option B, It is malware, not a virus but the malware includes viruses.
In option C, It doesn't install spyware on the user's computer.
In option E, It doesn't use for enterprise networks to penetrate.
Proxy server is a server that acts as a mediator between two systems.
One system can be your computer and the other can be the server to which you are asking a service, such as requesting a web page.
Lets suppose you request a web page from a server and you type a URL of a website to access a web page.
This request goes to proxy server which sends this request on your behalf to the target server in order to retrieve that web page.
Proxy server makes this request to the target server on the internet by using one of its IP addresses.
When the proxy server gets that web page, it will forward that web page to your requesting computer.
If you request a specific service such as a website frequently the proxy server saves that website on its cache.
So if you request that website again, proxy server will forward it to you from its cache rather than requesting it again from the target server on your behalf resulting in quick response to the user's request.
Proxy servers provide users with privacy to access the websites, and they can surf the internet anonymously .
