Types of Computer Viruses

If you’re system has been infected, you may want to learn a little more about what happened to your computer. You may find it interesting to learn that the term computer virus is actually a misnomer, since the type of infection depends on how it acts. There are several different types of computer infections. I’ll try to describe the most prevalent ones, in no particular order.

Trojan
This is type of infection generally looks like an innocuous program or file. It could be called something like helpme.exe or be part of a group of files with only one of them being the infected file. Generally trojans don’t reproduce themselves. Instead they open the door for other infection types. A trojan virus may contain a backdoor, allowing attackers and criminals access to your computer and files. It may contain a keylogger, which steals your credit and banking information, transmitting them to the originator of the infection.

Many times when a trojan is found on a computer system, many more infections are found as well. That is because the trojan will install other software as well. As such, there are several sub-types of trojans. The most common are: backdoor, exploit, rootkit, Trojan-Banker, Trojan-DDOS,  Trojan-Downloader, Trojan-Dropper, Trojan-FakeAV, Trojan-Game Thief, Trojan-IM, Trojan-Ransom, Trojan-SMS, Trojan-SPY, Trojan-Mailfinder.

The trojan types I have seen most personally are Trojan-FakeAV, which is a fake antivirus program which shows supposed infections, yet IT is the real infection. Trojan-Ransom, a program which modifies your computer system and/or files and demands money in order to relinquish your system. Finally, the rootkit, which hides infections and activities on a computer in an effort to avoid detection, allowing whatever illegal activity to continue as long as possible.

Worm
A worm is capable of spreading without any human interaction at all. Once your laptop or other system is infected with a worm, it may have MANY more infections. Not only your system but other systems will also be infected by the worm. One common example is spreading the worm to others on your email contact list.

Virus
A computer virus is linked to a program or file. Once run, it continues to spread, but ONLY through your actions. You may unknowingly be spreading a virus which is linked within a program. It can also infect other programs. A virus can destroy or alter data or it can simply display unwanted ads on your system. For instance, a virus may destroy your antivirus program, web browser, or other program. It could even make it so you can not open any file at all!

Bots
A bot is short for robot. These cute little infections will infect your system, known as the host, and report back to the criminal’s server. The automated processes will do such tasks such as: log keystrokes, relay spam, gather passwords, etc. They behave like a worm and self-replicate to other systems. Generally they do all this under the radar, in such a way as not to gain notice by the user.

Adware
This is the lowest type of infection, but it is not the least annoying. This type displays ads in your browser or even your desktop. Ads may not be what you are interested in, and are generally in favor of those who exploit the programs involved in their use. For instance, a criminal may gain revenue for displaying pornographic material to more people so they use adware to encourage unsuspecting users to check their sites out. In my experience however, adware is installed without users being aware of its existence. Search results and browsing habits are spied upon and ads are directed that benefit those who wrote the code.

Malware
This is a term which is short for malicious software. Any of the aforementioned infection types are malware.

Most infection types are installed through infected programs directly from a user desiring to install either free or hacked programs. Other infections occur even by the most diligent, since they can also come directly from a website, seemingly without any user interaction. Many times I hear a customer say that they didn’t install anything. Simply having your system online and going to a website can be thought of as a user interaction. Websites can take advantage of vulnerabilities in your browser and install malicious code. Other infections have been known to occur from just having your system online since their can be vulnerabilities in operating systems as well.

So how do you avoid all these types of infections? I like to employ three phases of protection.

1. The first, and best, is common sense. Avoid nefarious websites and read the screen and dialog boxes for programs you are installing that may be free. Many times the free programs disclose they are installing adware, and allow you to uncheck the box to do so. Other times, it does not, which leads to number two.
2. Use a GOOD antivirus program. I employ Kaspersky antivirus. I do NOT use the internet security suite, it is bloated and NOT needed. A one year license to the program is included in my service plan which is offered for $199, and includes a year of free virus removals.
3. Utilize a good firewall. Windows firewall is good, but I also like to use a firewall built into the router itself, as this is a connection to the internet that occurs BEFORE your computers.