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Virut removal


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#1 jason.r

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Posted 16 February 2011 - 04:19 PM

I know that when a machine is infected with virut that it can corrupt system files beyond repair.
Whenever a machine is logged onto that contains virut the .exe is already infected.
Since that is the case, would it be possible to log onto UBCD4Win and replace certain Windows system files, then run A/V software such as VirutKiller(any stand-alone virus removal tool) from UBCD4Win and get rid of virut?

Edited by Budapest, 16 February 2011 - 05:08 PM.
Moved from Virus, Trojan, Spyware, and Malware Removal Logs ~BP


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#2 Orange Blossom

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Posted 16 February 2011 - 05:41 PM

Hello,

That is not recommended in the case of Virut.

Virut is a dangerous polymorphic file infector with IRCBot functionality which infects .exe, .scr files, and opens a back door that compromises your computer. Using this backdoor, a remote attacker can access and instruct the infected computer to download and execute more malicious files.

-- Note: As with most malware infections, the threat name may be different depending on the anti-virus or anti-malware program which detected it. Each security vendor uses their own naming conventions to identify various types of malware.With this particular infection, the safest solution and only sure way to remove it effectively is to reformat and reinstall the OS.

Why? According to this Norman White Paper Assessment of W32/Virut, some variants can infect the HOSTS file and block access to security related web sites. Other variants of virut can even penetrate and infect .exe files within compressed files (.zip, .cab, rar). The Virux and Win32/Virut.17408 variants are an even more complex file infectors which can embed an iframe into the body of web-related files and infect script files (.php, .asp, .htm, .html, .xml). When Virut creates infected files, it also creates non-functional files that are corrupted beyond repair and in some instances can disable Windows File Protection. In many cases the infected files cannot be disinfected properly by your anti-virus. When disinfection is attempted, the files become corrupted and the system may become irreparable. The longer virut remains on a computer, the more critical system files will become infected and corrupt so the degree of damage can vary.

The virus disables Windows File Protection by injecting code into the "winlogon.exe" process that patches system code in memory.

CA Virus detail of W32/Virut

The virus has a number of bugs in its code, and as a result it may misinfect a proportion of executable files....some W32/Virut.h infections are corrupted beyond repair.

McAfee Risk Assessment and Overview of W32/Virut

There are bugs in the viral code. When the virus produces infected files, it also creates non-functional files that also contain the virus...Due to the damaged caused to files by virut it's possible to find repaired but corrupted files. They became corrupted by the incorrect writing of the viral code during the process of infection. undetected, corrupted files (possibly still containing part of the viral code) can also be found. this is caused by incorrectly written and non-function viral code present in these files.

AVG Overview of W32/Virut

Virut is commonly spread via a flash drive (usb, pen, thumb, jump) infection using RUNDLL32.EXE and other malicious files. It is often contracted by visiting remote, crack and keygen sites. These type of sites are infested with a smörgåsbord of malware and a major source of system infection.

...warez and crack web pages are being used by cybercriminals as download sites for malware related to VIRUT and VIRUX. Searches for serial numbers, cracks, and even antivirus products like Trend Micro yield malcodes that come in the form of executables or self-extracting files...quick links in these sites also lead to malicious files. Ads and banners are also infection vectors...

Keygen and Crack Sites Distribute VIRUX and FakeAV

However, the CA Security Advisor Research Blog have found MySpace user pages carrying the malicious Virut URL. Either way you can end up with a computer system so badly damaged that recovery is not possible and it cannot be repaired. When that happens there is nothing you can do besides reformatting and reinstalling the OS.

Since virut is not effectively disinfectable, your best option is to perform a full reformat as there is no guarantee this infection can be completely removed. In most instances it may have caused so much damage to your system files that it cannot be completely cleaned or repaired. In many cases the infected files (which could number in the thousands) cannot be deleted and anti-malware scanners cannot disinfect them properly. Security vendors that claim to be able to remove file infectors cannot guarantee that all traces of it will be removed as they may not find all the remnants. If something goes awry during the malware removal process there is always a risk the computer may become unstable or unbootable and you could loose access to all your data.

Further, your machine has likely been compromised by the backdoor Trojan and there is no way to be sure the computer can ever be trusted again. It is dangerous and incorrect to assume the computer is secure even if your anti-virus reports that the malware appears to have been removed.

Many experts in the security community believe that once infected with this type of malware, the best course of action is to reformat and reinstall the OS. Reinstalling Windows without first wiping the entire hard drive with a repartition and/or format will not remove the infection. The reinstall will only overwrite the Windows files. Any malware on the system will still be there afterwards. Please read:

Whenever a system has been compromised by a backdoor payload, it is impossible to know if or how much the backdoor has been used to affect your system...There are only a few ways to return a compromised system to a confident security configuration. These include:
• Reimaging the system
• Restoring the entire system using a full system backup from before the backdoor infection
• Reformatting and reinstalling the system

Backdoors and What They Mean to You

This is what security expert miekiemoes' has to say: Virut and other File infectors - Throwing in the Towel?

If I guide someone with Virut (or any other File Infector) present and their Antivirus cannot properly disinfect it, then I recommend a format and reinstall...dealing with such infections is a waste of time and that's why I prefer the fastest and safest solution - which is a format and reinstall...After all, I think it would be irresponsible to let the malware "stew" (download/spread/run more malware) for another couple of days/weeks if you already know it's a lost case.

This is what Jesper M. Johansson at Microsoft TechNet has to say: Help: I Got Hacked. Now What Do I Do?.

The only way to clean a compromised system is to flatten and rebuild. That’s right. If you have a system that has been completely compromised, the only thing you can do is to flatten the system (reformat the system disk) and rebuild it from scratch (reinstall Windows and your applications).


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#3 Eric3301

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Posted 16 February 2011 - 07:19 PM

Isn't it possible to use Dr. Web's Live CD to clean the infection? It cleans infected files instead of deleting them and removes most of the virus, enough that you can download and utilize more tools after.

#4 Budapest

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Posted 16 February 2011 - 07:25 PM

To quote the above:

In many cases the infected files cannot be disinfected properly by your anti-virus. When disinfection is attempted, the files become corrupted and the system may become irreparable.

Dr. Web's Live CD may also corrupt the files it tries to disinfect.
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#5 boopme

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Posted 16 February 2011 - 07:51 PM

Hello...
If you insist on trying to fix this infection instead of following our advice to reformat and reinstall your operating system, there are some tools and various rescue disks available from several anti-virus vendors. Keep in mind there is no guarantee the repair will be successful and you may need to try more than one. Even vendors like Kaspersky say there is no guarantee that some files will not get corrupted during the disinfection process. This means that infected executables and system files can become unusable after attempting to repair them and there's still no quarantee the virus is really gone. Since many of these are legitimate critical files required by the operating system, deletion is not a viable option. This destructive behavior may be by design as explained in File Infectors: To Junk Or Not To Junk.

In my experience, users may find their system performing better for a short time after attempted disinfection only to have it become progressively worst again as the malware continues to reinfect thousands of files. Some folks will try every tool or rescue disk they can find in futile attempts to repair critical system files. If something goes awry during the malware removal process the computer may become unstable or unbootable and you could loose access to all your data. In the end most folks end up reformatting out of frustration after spending hours attempting to repair and remove the infected files.

Bleeping Computer DOES NOT assume any responsibility for your attempt to repair this infection using any of the following tools. You do this at your own risk and against our advice.

If your computer is bootable, disinfection can be attempted through a combination of the following tools:These are links to Anti-virus vendors that offer free LiveCD or Rescue CD utilities that are used to boot from for repair of unbootable and damaged systems, rescue data, scan the system for virus infections. Burn it as an image to a disk to get a bootable CD. All (except Avira) are in the ISO Image file format. Avira uses an EXE that has built-in CD burning capability.

If you are not sure how to burn an image, please read How to write a CD/DVD image or ISO. If you need a FREE utility to burn the ISO image, download and use ImgBurn.
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#6 quietman7

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Posted 16 February 2011 - 09:24 PM

Isn't it possible to use Dr. Web's Live CD to clean the infection?


I'm sorry but IMO that is wishful thinking. I do not know of any security vendor who will guarantee complete removal of file infectors. Even vendors like Kaspersky say there is no guarantee that some files will not get corrupted during the disinfection process. This means that infected executables and system files can become unusable after attempting to repair them and there's still no quarantee the virus is really gone. Since many of these are legitimate critical files required by the operating system, deletion is not a viable option. This destructive behavior may be by design as explained in File Infectors: To Junk Or Not To Junk.

In my experience, users may find their system performing better for a short time after attempted disinfection only to have it become progressively worst again as the malware continues to reinfect thousands of files. Some folks will try every tool or rescue disk they can find in futile attempts to repair critical system files. If something goes awry during the malware removal process the computer may become unstable or unbootable and you could loose access to all your data. In the end most folks end up reformatting out of frustration after spending hours (and days) attempting to repair and remove the infected files.

That's why most security experts say the best course of action is to wipe the drive clean, reformat and reinstall the OS.
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