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Backdoor.Agent won't stay removed


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#1 veseng

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Posted 22 October 2011 - 02:34 AM

I seem to have an infection that Malwarebytes calls Backdoor.Agent It tries to remove it but after the suggested reboot it comes back, after running in normal mode and in safe mode. MS Forefront does not detect it.

One oddity is that the BIOS start-up screen now has the following as the last line of the screen:

05/15/2009-Bear Lake-6A79OFKOC-00

I am running Windows 7 Ultimate X64

The relevant part of the Malwarebytes log:

Registry Values Infected:
HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon\Shell (Backdoor.Agent) -> Value: Shell -> Delete on reboot.


Last Sunday, Forefront detected and removed "Exploit:JS/Blacole.N" if that's relevant.

Any help would be appreciated.

Thanks for the Bleeping Computer.

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#2 boopme

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Posted 22 October 2011 - 09:15 AM

Hello veseng

First a note on these backdorr infections.

This allows hackers to remotely control your computer, steal critical system information and download and execute files.

I would counsel you to disconnect this PC from the Internet immediately. If you do any banking or other financial transactions on the PC or if it should contain any other sensitive information, please get to a known clean computer and change all passwords where applicable, and it would be wise to contact those same financial institutions to apprise them of your situation.

Though the trojan has been identified and can be killed, because of it's backdoor functionality, your PC is very likely compromised and there is no way to be sure your computer can ever again be trusted. Many experts in the security community believe that once infected with this type of trojan, the best course of action would be a reformat and reinstall of the OS. Please read these for more information:

How Do I Handle Possible Identify Theft, Internet Fraud and CC Fraud?
When Should I Format, How Should I Reinstall

We can still clean this machine but I can't guarantee that it will be 100% secure afterwards. Let me know what you decide to do.

To clean it...

Please go here....
Preparation Guide ,do steps 6 - 9.

Create a DDS log and post it in the new topic explained in step 9,which is here Virus, Trojan, Spyware, and Malware Removal Logs and not in this topic,thanks.
If Gmer won't run,skip it and move on.
Include a link back to this topic.

Let me know if that went well.
How do I get help? Who is helping me?For the time will come when men will not put up with sound doctrine. Instead, to suit their own desires, they will gather around them a great number of teachers to say what their itching ears want to hear....Become a BleepingComputer fan: Facebook

#3 veseng

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Posted 24 October 2011 - 01:16 AM

Thanks for the reply.

OK, I think you are recommending a reformat and reinstall so that is what I'll do. This would be a good time to install a larger HDD so I'll so I'll use that. Is it OK to reformat the drive in the infected computer and to copy the system backup partition to the new drive?

I think my question should be is it likely the MBR of the factory installed recovery partition has been infected with whatever malware I have?

Again, thanks for Bleeping Computer.

#4 boopme

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Posted 25 October 2011 - 12:05 PM

Yes I am. Reformatting a hard disk deletes all data. If you decide to reformat, you can back up all your important documents, data files and photos. The safest practice is not to backup any autorun.ini or .exe files because they may be infected. Some types of malware may disguise itself by adding and hiding its extension to the existing extension of files so be sure you take a close look at the full name. After reformatting, as a precaution, make sure you scan these files with your anti-virus prior to copying them back to your hard drive..

Caution: If you are considering backing up data and reformatting, keep in mind, with a Virut infection, 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), 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, .ini, .htm, .html, .php, .asp, .xml, .zip, .rar, .cab as they may be infected.

If you're not sure how to reformat or need help with reformatting, please review:These links include step-by-step instructions with screenshots:Vista users can refer to these instructions:Don't forget you will have to go to Microsoft Update and apply all Windows security patches after reformatting.

Note: If you're using an IBM, Sony, HP, Compaq or Dell machine, you may not have an original XP CD Disk. By policy Microsoft no longer allows OEM manufactures to include the original Windows XP CD-ROM on computers sold with Windows preinstalled. Instead, most computers manufactured and sold by OEM vendors come with a vendor-specific Recovery Disk or Recovery Partition for performing a clean "factory restore" that will reformat your hard drive, remove all data and restore the computer to the state it was in when you first purchased it. See Technology Advisory Recovery Media. If the recovery partition has become infected, you will need to contact the manufacturer, explain what happened and ask them to send full recovery disks to use instead..

If you need additional assistance with reformatting or partitioning, you can start a new topic in the Operating Systems Subforums forum.
How do I get help? Who is helping me?For the time will come when men will not put up with sound doctrine. Instead, to suit their own desires, they will gather around them a great number of teachers to say what their itching ears want to hear....Become a BleepingComputer fan: Facebook




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