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Infected with Win32.Nimnul.A


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#1 draven

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Posted 05 March 2011 - 07:19 PM

Hello,

My KIS detected this and looked like it removed but it comes coming back. Im on Vista and running a MBAM full scan now.

Please help.

Thanks

Edited by draven, 05 March 2011 - 07:33 PM.


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#2 quietman7

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Posted 05 March 2011 - 10:45 PM

I'm afraid I have very bad news.

Win32.Nimnul.a is the name used by Kaspersky for variants of Win32/Ramnit.A / Win32/Ramnit.B, a dangerous file infector with IRCBot functionality which infects .exe, and .HTML/HTM 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. The infected .HTML or .HTM files may be detected as The infected .HTML or .HTM files may be detected as Virus:VBS/Ramnit.A or VBS/Generic. Win32/Ramnit.A!dll is a related file infector often seen with this infection. It too has IRCBot functionality which infects .exe, .dll and .HTML/HTM files and opens a back door that compromises your computer. This component is injected into the default web browser by Worm:Win32/Ramnit.A which is dropped by a Ramnit infected executable file.

-- 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? The malware injects code in legitimate files similar to the Virut virus and in many cases the infected files (which could number in the thousands) cannot be disinfected properly by your anti-virus. When disinfection is attempted, the files often become corrupted and the system may become unstable or irreparable. The longer Ramnit.A remains on a computer, the more files it infects and corrupts so the degree of damage can vary.

Ramnit is commonly spread via a flash drive (usb, pen, thumb, jump) infection where it copies Worm:Win32/Ramnit.A with a random file name. The infection 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.

In my opinion, Ramnit is not effectively disinfectable, so 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. 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 wipe the drive clean, reformat and reinstall the OS. 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 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).


Important Note:: If your computer was used for online banking, has credit card information or other sensitive data on it, all passwords should be changed immediately to include those used for banking, email, eBay, paypal and any online activities which require a username and password. You should consider them to be compromised and change passwords from a clean computer, not the infected one. If not, an attacker may get the new passwords and transaction information. Banking and credit card institutions should be notified immediately of the possible security breach. Failure to notify your financial institution and local law enforcement can result in refusal to reimburse funds lost due to fraud or similar criminal activity. If using a router, you need to reset it with a strong logon/password so the malware cannot gain control before connecting again.
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#3 draven

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Posted 06 March 2011 - 12:53 PM

Thanks for the reply.

Am i still able to use my USB drive to backup my data?

#4 quietman7

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Posted 06 March 2011 - 01:01 PM

If you are considering backing up data and reformatting or doing a factory restore with a vendor-specific Recovery Disk/Recovery Partition due to malware infection, keep in mind with file infectors, there is always a chance of backed up data reinfecting your system. If the data is important to you, then you can try to salvage some of it but there is no guarantee so be forewarned that you may have to start over again afterwards if reinfected by attempting to recover your data. Only back up your important documents, personal data files, photos to a CD or DVD drive, not a flash drive or external hard drive as they may become compromised in the process. The safest practice is not to backup any executable files (*.exe), screensavers (*.scr), dynamic link library (*.dll), autorun (*.ini) or script files (.php, .asp, .htm, .html, .xml) files because they may be infected by malware. Avoid backing up compressed files (.zip, .cab, .rar) that have executables inside them as some types of malware can penetrate compressed files and infect the .exe files within them. Other types of malware may even disguise itself by hiding a file extension or adding to the existing extension as shown here (click Figure 1 to enlarge) so be sure you look closely at the full file name. If you cannot see the file extension, you may need to reconfigure Windows to show file name extensions. Then make sure you scan the backed up data with your anti-virus prior to to copying it back to your hard drive.

If your CD/DVD drive is unusable, another word of caution if you are considering backing up to an external usb hard drive as your only alternative. External drives are more susceptible to infection and can become compromised in the process of backing up data. I'm not saying you should not try using such devices but I want to make you aware of all your options and associated risks so you can make an informed decision if its worth that risk.Again, do not back up any files with the following file extensions: exe, .scr, .dll, .ini, .htm, .html, .php, .asp, .xml, .zip, .rar, .cab as they may be infected.
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#5 draven

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Posted 06 March 2011 - 01:34 PM

If the files are media data - music etc, can i use USB or would it be best to use data discs?

#6 quietman7

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Posted 06 March 2011 - 04:16 PM

CD/DVDs.
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#7 draven

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Posted 07 March 2011 - 12:36 PM

It seems the virus has stopped, KIS stopped detecting it last night after i deleted a program called PC Doctor from Program Files which was infected.

Is this normal for this virus to stop and come back? It's been almost 24 hours since it happened.

The best course of action is still to reinstsll my PC i guess.

#8 quietman7

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Posted 07 March 2011 - 02:53 PM

I do not know of any security vendor who will guarantee complete removal of file infectors since 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 afterward, there is still no guarantee the virus is really gone. Since many of the affected files are legitimate critical files required by the operating system, deletion is not a viable option. Kaspersky even admits that some malicious programs cannot be disinfected by their products in this support article which provides some suggestions for dealing with file infectors. The destructive behavior by this type of malware 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.

...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.

miekiemoes' Blog: Virut and other File infectors - Throwing in the Towel?

These are comments from some of the major anti-virus vendors in regards to file infectors:

...In many cases, files cannot simply be deleted as this would affect the stability or even basic functionality of the operating system and other software. Instead, the infected host program must be disinfected by removing the virus code from it and by carefully restoring the original contents and file structure if possible. This means detection and removal are still an issue for antivirus software....

Avira: Cleaning polymorphic infected files

...for infected users we have to offer no hope - fdisk - format and re-install is the only solution open to them...

avast: a file infector and why we cannot give false hope!

...it injects its code into running processes...The virus has a number of bugs in its code, and as a result it may misinfect a proportion of executable files...unfortunately, some infections are corrupted beyond repair.

McAfee: polymorphic infector

The suggestions in this article are not intended to 100% guarantee removal of all threats...The file infector employs a technique to make sure its corrupted .DLL format will replace the targeted extensions found within the system. When the computer is rebooted it incidentally boots the infected file and continues its advancement throughout the system...

Norton (Symantec): File infector

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...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: polymorphic infector

...you can try via rescue cd, or slave mounted hard drive. but there's no guarantee that some files won't get corrupted through the disinfection process.

Kaspersky: file infector

Edited by quietman7, 07 March 2011 - 02:58 PM.

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#9 draven

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Posted 07 March 2011 - 05:12 PM

Thanks.

When the virus was active i connected my flash drive and some folders went on to it, does this mean i can't use that flash drive any more? Can i use Flash Disinfector to fix it?

I have now turned off Autoplay.




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