DyFuCA.Internet.Optimizer

Adware

Software that is designed to launch advertisements, frequently pop-up ads, on a user’s computer and/or to redirect search results to promotional Web sites. Adware programs are often built into freeware or shareware programs, where the adware creates an indirect ‘charge’ for using the free program. Sometimes a trojan can silently download an adware program from a Web site and install it onto a user’s machine.

Hacker tools, or Browser Hijackers, can also download an adware program by exploiting a web browser’s vulnerability. Browser Hijackers may tamper with the browser settings, redirect incorrect or incomplete URLs to unwanted Web sites, or change the default home page. They can also re-direct a user’s searches to “pay-to-view” (often pornographic) Web sites.

Typically, many adware programs do not leave any marks of their presence in the system: they are not listed on Start | Programs; they add no icons to the system tray; and they don’t show up on the task list. In addition, adware programs seldom provide an uninstallation procedure, and attempts at manually removing them frequently result in failure of the original carrier program.

BHO

Browser Helper Object, or BHO, is a dynamic link library (DLL) that runs whenever Internet Explorer is started. Generally, BHOs are included in installation of third-party programs where they are offered as enhancements of the browser functionality. For example, many Internet Explorer plug-ins are in essence BHOs.

BHOs can be installed silently or “legitimately” when a user fails to read the fine print included in the freeware program’s EULA (End User License Agreement).

Because BHOs are small programs, they can do anything that other programs can do. It’s not easy to detect the BHOs installed on the computer. This enables hackers and other malevolent users to employ the BHO functionality in their interests, for example, secretly install adware programs or gather various statistics on the user’s browsing trends.

Backdoor

Of all trojans, backdoor trojans pose the greatest danger to users’ PCs because they give their authors remote control over infected computers. They are downloaded, installed, and run silently, without the user’s consent or knowledge. Upon installation, backdoor trojans can be instructed to send, receive, execute and delete files, gather and transfer confidential data from the computer, log all activity on the computer, and perform other harmful activities.

Hijacker

Software that seizes control of a computer’s resources to proliferate itself or use them for other malicious purposes.
There are several types of hijackers. The most common are:

• Browser hijackers – Alters the existing Internet browser settings so that a user is redirected to unwanted or malicious Web sites. These include programs that change the browser Home page or replace a popular search service’s home page with its own fake copy, whose search results point to particular malicious or irrelevant sites.
• Autorun hijackers – Automatically run certain programs on start-up of a user’s computer.

Downloader

A type of trojan. The primary purpose of downloaders is to install malicious code on a user’s computer. However, they can enable other malicious uses. For example, they can be used to continually download new versions of malicious code, adware, or “pornware.” They are also used frequently used to exploit the vulnerabilities of Internet Explorer.

Downloaders are typically written in script languages such as VBS or JavaScript.