How Trojans Spread

A trojan virus uses multiple ways to spread over the Web and replicate itself. That's why if you want to know how to remove the trojan virus, you need to be aware of the ways it infects target computers.

1. Through email attachments. Probably the oldest method of mass distribution, it has grown into a new industry of virus propagation. Modern sophisticated software, dedicated servers, large networks of already infected personal computers are used to send out gazillions of spam emails each and every day. A trojan virus may be attached as a greeting card, wallpaper, animated image, screensaver. Many of them have subjects with "hi, here's a greeting card for you!" words.
2. Once downloaded and executed, a trojan may use the address book to send itself to other computers. That's why it is still worth noting that emails from unknown addresses should never be opened.
3. Trojans widely exploit messaging software, especially popular programs like MSN Messenger/Live Messenger, Yahoo! Messenger, Skype, etc.
4. Trojans may be included into bundles of emoticons for email clients and instant messengers alike.
5. Modern Trojan viruses widely exploit security breeches in Windows Operating system and the popularity of multimedia content available online. For example, zlob trojan, responsible for aggressive distribution of over a hundred of fake antispyware programs, used video codecs to install onto target computers. Whenever a surfer visited a website with embedded malicious code, a window would pop-up asking to install a video codec in order to display a movie. Once the visitor clicked to agree to installation, trojan Zlob infected the system immediately.

A Trojan Virus generates fake alerts]

Trojans and Rogue Security Software

Trojans have gained an even worse reputation because of rogue security software which they distribute. Rogue software are bogus programs that pretend to look and act like antivirus or antispyware applications, various system maintenance tools, registry cleaners, etc. They use fake malware scan results and persistent pop-ups trying to scare the user into paying for a "full version" of the program. However, even getting a license key in exchange for some $30 or $100 changes nothing in the way rogue security software behaves. Even annoying pop-ups continue to appear on the desktop at same intervals.
I believe many people became more aware of Web threats thanks to rogue programs, because they got interested in the nature of this phenomenon, which led them to learn something about how to remove a trojan virus.
source: hubpages.com

What is a Trojan Virus

BitDefender, a world renowned antivirus software maker, conducted a research based on its statistics. Its purpose was to show which types of threats dominate the Web. The results are shown on the screenshot to the right. -->
It's clearly seen that nine out of ten most encountered threats are trojan viruses.
The first trojan in the list, Trojan.Clicker.CM, displays commercial ads, which "eat" the bandwidth and, as a consequence, slow down the PC.
It should be pretty evident that methods to remove trojan viruses should quickly adapt to the reality, since trojans lead the malware army.
So before learning how to remove trojan virus, it is important to know what this type of malware is in essence.
In short, as the term suggests, a trojan pretends to look and act like it's a legit Windows application. However, its malicious code is programmed to execute operations that no PC owner would want on his computer. 

• Trojans are capable of stealing important information (passwords, credit card numbers, etc.) Then the sensitive data is transmitted over the Web to virus creators, who then are able to take control over infected computers. 
• A considerable slow-down in system performance is one of the consequences of trojan virus infection.
• A user may be distracted by unexpected pop-ups with ads (mostly with casino, poker, adult content).
• Trojan viruses attempt to become parts of the infected system by interacting with Windows processes and injecting malicious code into legitimate files executed by the operating system (Winlogon is an example of such injection when a trojan virus is fully loaded after the user enters login details).

Trojans may get involved into distribution of unsolicited emails. Sometimes this type of malware is responsible for attacks on other computers connected to the Internet. While it's a bit scary, in fact any PC infected by a trojan virus may be engaged in decentralized attacks on servers of government institutions, universities, etc.

How to Remove Trojan Virus

Why is it difficult to remove trojan virus

Because trojans are a very common type of malware that is known to practically all web surfers, it is clear how hard it is to answer the question "how do i remove a trojan virus from my computer?"

A trojan virus makes a PC user think that it is a beneficial Windows application. Thus, trojans often masquerade as screensavers, packages of video codecs, tray clocks, weather forecast software, messengers, etc. Another major source of trojans is all kinds of illegal programs, cracks and keygens. It is a common practice to include trojans into free antivirus software distributed via peer-to-peer networks (e.g. torrents). This is especially dangerous for end-users because antivirus program cannot detect a trojan before the installation finishes and all updates are downloaded, thus the use of free antivirus software downloaded from suspicious websites or sources imposes a great risk on personal computers.

Moreover, one of the most difficult things in PC maintenance is to remove trojan virus from a PC where software of a suspicious origin has been installed. 

TOP-10 Internet Threats (July, 2008), by: BitDefender, www.bitdefender.com

While it is possible to remove trojan virus manually, the set of steps involved in PC cleaning requires a decent level of computer experience. There's a need to indentify the type of malware, to locate infected or harmful files and registry entries, to download the tools that will help to remove trojan virus.

A common practice implies the use of special software, commonly referred to as 'trojan removers'. It is however important to point out that this type of programs makes a considerable part of antispyware software market, which is a big incentive for some programmers to make quick money by releasing trojan removers with mediocre scanning engines, poor algorithms, and no support.

Therefore I feel it's necessary to warn you, the readers of this hub, that the decision about preferable trojan remover should be done after at least basic research of the available programs. User feedback and reviews are important sources of information, though the quality of reviews of trojan removers often leaves much to be desired.

NOTE: Every program recommended in this hub is 100% safe to use. I give as detailed descriptions as possible, with an accent on vital features not to be found in competitors' software. Same applies to any download links given below.

Some folks prefer to remove trojan virus for free. I myself am a big fan of freeware tools, but there's a big problem here. Some developers of scam software promote their products as free trojan virus removers, to entice web surfers into downloading and installing them. However, such free trojan removers are often more dangerous than trojans. Even scanning of executable files by antivirus programs may show them as clean. This is yet another reason why I advise to make some research before downloading and installing any software that promises to help to remove trojan virus.

Online scanners are an absolutely safe and free way to remove trojan virus. All major antivirus software makers offer online virus scanners on their websites, and these services are available for everybody enjoying a stable Internet connection. Not all of the scanners have same detection rate, and they differ in types of malware they're able to remove.

For trojan viruses involved in the distribution of rogue security programs, there are special tools developed by volunteers. These tools have a very specific targeting and are meant to fight either certain trojans, or a range of malware. Usually such tools are created because major antivirus and antispyware companies fail to address new threats quickly. This happens either due to bugs in scan engines, or requires significant updates.

Command-line anti-malware scaners present another way to remove trojan virus for free. Sadly, I was able to find only two completely free and available scanners: TrendMicro SysClean and a-squared anti-malware command-line scanner. The latter is suitable for PC users with intermediate experience, while TrendMicro software is aimed at advanced users or system administrators.

source: hubpages.com

How to Remove Trojan Win32 Off Cmd

By Ian King, eHow Contributor

updated: May 5, 2010

Win32.dll is a Dynamic Link Library (DLL) file used by the backdoor Trojan known as Trojan.Back.door.IROffer. Removing the Win32.dll file from the Command Prompt (cmd) is necessary to remove the backdoor Trojan. If not removed, it can download additional Trojans onto your computer, slow your computer and allow hackers to access your personal information.

Instructions

1. Click on the "Start" menu.
2. Click on "Run.
3. Type "cmd" into the open box. The Command Prompt window will open
4. Type "regsvr32 /u system32.dll" into the Command Prompt window and press "Enter.
5. Restart your computer

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How to Remove a Trojan Virus Permanently

By Matthew Schieltz, eHow Contributor

updated: January 28, 2010

Trojan horses are malicious programs that may appear to be legitimate but actually harm your computer. Trojans place unusual and unremovable icons on your desktop and some take control of your computer. Many disable functions and programs like the Windows Task Manager. It is often necessary to use multiple techniques to remove a Trojan virus permanently.

Difficulty: Moderately Easy

Instructions

1. Download and install an anti-malware or antivirus program that handles Trojan viruses. Malwarebytes' anti-malware is one such program and was recommended by CNET editors in April 2009; this program removes stubborn viruses and Trojans that other typical antivirus programs cannot remove.
   
2. Run the anti-malware program on your computer. Choose the full scan option so that the program scans all your hard drives as well as hidden files and folders. Close all other programs while the anti-malware program is running so that it operates quickly and efficiently.
   
3. Review the results that the anti-malware program displays. Choose the option to "delete" or "remove" infected files that contain Trojan viruses. Take note of any files that the program was not able to eradicate as these should be listed; the program may list DLL files or similar directories where the Troan resides.
   
4. Open the command prompt box to remove any DLL files of the Trojan. Click on "Start," then "Run," type in "cmd," and hit "Enter" to open the command prompt box. Type "cd" followed by the directory in which the Trojan is located. To unregister the DLL file, type the command "regsvr32 /u <filename>.dll" where <filename" is the name of Trojan DLL file. Close the command prompt box.
   
5. Open the Windows Registry to remove Trojan-infected registry files. Click on "Start," then "Run," type in "regedit" in the command prompt box to open it. Look for and delete the registry files infected by the Trojan virus. Go to McAfee's free virus information at "home.mcafee.com/virusInfo/" to find the latest, updated information on Trojan viruses and which registry entries could possibly be infected.
   
6. Confirm that the Trojan virus has been deleted. Perform a full scan using an anti-malware or antivirus software program. Check the results of the scan. Make sure that there are no Trojans or viruses listed as files unable to be removed by the program.

source: www.ehow.com

How to Remove a Trojan Virus

By an eHow Contributor

A Trojan virus is faulty computer program that can infect remote computer by changing the desktop or deleting important files. Generally called a Trojan Horse, it appears as a legitimate file or software from a trusted source, therefore tricking users into opening it or downloading it. Take action and protect your personal computer files by learning to delete this Trojan virus.

Difficulty: Moderate

Instructions

1. 1
   Reboot your computer if you have a Mac. Do this by holding down the "Shift" key while the computer restarts itself.
   
2. 2
   Launch an antivirus program that you should have installed on your computer, such as Symantec's Norton or McAfee. Wait for the program's window to appear, then go to "Disk View." Highlight your computer, then select "Scan/Repair" so that the antivirus can detect the Trojan and trash it.
   
3. 3
   Exit the antivirus program on your Mac. Restart your computer again to ensure that the Trojan has been deleted. Empty the trash can on your computer once it is back up and running.
   
4. 4
   Disable the System Restore feature if you're a Windows user. Go to "Start" at the bottom of your screen, then right-click the "My Computer" icon to go to "Properties." Check "Turn off System Restore" under the System Restore tab in the "Properties" window, then select "Apply." Confirm that you want to disable System Restore by clicking "Yes" and "OK."
   
5. 5
   Update your virus definitions in your antivirus program. Open the program, or go to the website, to download the latest definitions so that you can receive the most recent alerts and keep your computer protected.
   
6. 6
   Scan your files to detect the Trojan file. Follow the instructions in your antivirus program to delete any suspicious files. You may want to write down the path and file name of the Trojan, which is usually found in the "C:\" hard drive. Then, edit your computer's backup registry by choosing "Start," then "Run." Type "regedit" in the window that appears and click "OK."
   
7. 7
   Search for the registry entry from which the Trojan derived, which may begin with "HKEY" followed by the file path. Delete the registry entry to ensure that the Trojan is removed. Exit the registry entry, and restart your computer so that the changes can take effect.
   

Tips & Warnings

• After you've removed the Trojan and restarted your computer, remember to turn the System Restore function back on. Follow Step 4, then uncheck "Turn off System Restore," then "Apply." Confirm that you want to turn on the feature, then hit "OK."
   
  source: ehow.com