Trojan
A trojan, or "trojan horse" is not really a virus, but it does behave like one. A trojan is a malicious piece of software that is introduced to the computer by an action of the user. It arrives as an email attachment or as part of a program, and under the guise of performing an actual function or doing something else, is introduced to the system by being installed by a user on that system.
Once in the computer, a trojan often opens a "back door" to allow remote access to the computer by the originators of the trojan.
A trojan gets its name from the legend of the Trojan Horse, which came in through the front gates while secretly containing an invading army.
Content Filters
Content filters are programs that restrict access by system users to certain Internet content, such as specific websites or categories of websites. Such content filtration is increasingly being used in schools to restrict student access to social networking sites, and in businesses to limit use of the company network for personal web surfing.
