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Nimnul.A reappears


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#1 carlstars

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Posted 22 October 2010 - 10:09 AM

Hi

Recently I opened my scanner software (not used very often) and all of a sudden I had my pareto antivirus flashing away like mad saying that it had blocked the nimnul.a virus and then reccommended that I do a full scan of my system

On doing so it found over 1000 infections of this virus. I then cleaned them and rebooted. On doing so it found hundreds of them again..they wont go away

I have downloaded combofix but not run it yet

Please help

Regards

Carl

Edited by carlstars, 22 October 2010 - 10:32 AM.


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#2 quietman7

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Posted 22 October 2010 - 06:00 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, file infectors 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 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).


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#3 carlstars

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Posted 25 October 2010 - 02:03 AM

OMG....Nightmare!

What about all the files that I currently have and need to keep?

Particularly databases etc

#4 quietman7

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Posted 25 October 2010 - 07:15 AM

Caution: 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 that 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.

Important: Since many file infectors are spread by using infected removable usb flash drives and external drives, before starting the backup and restore process you should disable autorun. Why? This type of infection usually involves malware that modifies/loads an autorun.inf (text-based configuration) file into the root folder of all drives (internal, external, removable) along with a malicious executable. When removable media is inserted (mounted), autorun looks for autorun.inf and automatically executes the malicious file to run silently on your computer.

Keeping autorun enabled on USB (pen, thumb, jump) and other removable drives has become a significant security risk due to the increasing number of malware variants that can infect them and transfer the infection to your computer. To learn more about this risk, please read:Many security experts recommend you disable Autorun as a method of prevention. Microsoft recommends doing the same.

...Disabling Autorun functionality can help protect customers from attack vectors that involve the execution of arbitrary code by Autorun when inserting a CD-ROM device, USB device, network shares, or other media containing a file system with an Autorun.inf file...

Microsoft Security Advisory (967940): Update for Windows Autorun

For most novice users, the easiest way to inoculate a flash drive is to create a Read-only folder on the drive, name it autorun.inf and set file permissions to restrict changes as described by Trend Micro in How to Maximize the Malware Protection of Your Removable Drives. This folder will help protect your drives from future infection by keeping the autorun file from being installed on the root drive and executing malicious files.

You can download and use tools like Autorun Eater or Autorun USB Virus Finder which will allow removal of any suspicious 'autorun.inf' files they find. Panda USB Vaccine allows for computer and usb vaccination.
  • Computer Vaccination will prevent any AutoRun file from running, regardless of whether the removable device is infected or not.
  • USB Vaccination disables the autorun file so it cannot be read, modified or replaced and creates a hidden AUTORUN_.INF on the flash drive partition as protection against malevolent code by preventing a malicious autorun file from being installed. The Panda Resarch Blog advises that once USB drives have been vaccinated, they cannot be reversed except with a format. If you do this, be sure to back up your data files first or they will be lost during the formatting process.
As an added precaution, hold down the Shift key when inserting the drive into the computer containing the data to be backed up until Windows detects it in order to keep autorun.inf from executing automatically.
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#5 kokeip

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Posted 19 November 2010 - 11:14 AM

Carls, what did u do with the win32.nimnul.a.?
I´ve the same problem, and i´m trying to go about it with a kaspersky resue disk.

Let my know if u had to reformat the pc.

Thanks.

#6 quietman7

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Posted 19 November 2010 - 12:04 PM

Welcome to BC kokeip

If you have an issue or problem you would like to discuss, please start your own topic. Doing that will help to avoid the confusion that often occurs when trying to help two or more members at the same time in the same thread. Even if your problem is similar to the original poster's problem, the solution could be different based on the kind of hardware, software, system requirements, etc. you are using and the presence of other malware. Further, posting for assistance in someone else's topic is not considered proper forum etiquette.

Thanks for your cooperation.
The BC Staff

FYI: I do not know of any security vendor who will guarantee complete removal of file file infectors. Even vendors like Kaspersky say there is no guarantee that some files will not get corrupted during the disinfection process. 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.
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