Win32.Delf

A trojan is a program that is disguised as legitimate software but is designed to carry out some harmful actions on the infected computer.

Unlike viruses and worms, trojans don’t replicate but they can be just as destructive.

These days trojans are very common. Trojans are divided into a number different categories based on their function or type of damage.

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.

Spyware is designed to gather data from a computer and transfer it to a third party without the consent or knowledge of the computer’s owner. This includes collecting confidential information (passwords, credit card numbers, PIN numbers, etc.), monitoring key strokes, gathering e-mail addresses, or tracking surfing habits. Such resource-consuming activities slow down the system and generally impact the computer’s performance.

“Spyware” is an umbrella term for a diverse group of malware-related programs, rather than a clear-cut category. Most spyware definitions apply not only to adware, pornware and ‘riskware’ programs, but to many trojans as well.

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.

Remote Access Tool. A program that enables a hacker to remotely access and control other people’s computers. A RAT can serve a variety of malicious purposes, including hijacking and transferring private information, downloading files, running programs, and tampering with system settings.

Hacker tools are utilities designed to help hackers gain control of remote computers in order to use them as zombies (in DoS attacks, for example), download other malicious programs into those computers, or use them for other malicious purposes.

A DoS (Denial of Service) attack is designed to disrupt or stop the normal running of a Web site, server, or other network resource. Hackers or malware writers resort to various ways to achieve this. A DoS attack can commonly result in a server being flooded with more network traffic than it is capable of processing. This hinders or prevents the server’s normal operation and sometimes causes its complete failure.

Unlike a DoS attack, a DDoS attack employs multiple PCs. The hacker or malware writer normally uses one infected computer - “master” - to centrally coordinate the attack across other, so-called “zombie”, computers. Typically, the malware writer gains control of both master and zombie computers by exploiting a weakness in an application or the operating system on those computers, in order to install a trojan or other malicious code.