1. Symantec/
  2. Security Response/
  3. W32.Kernelbot.A


Risk Level 2: Low

November 3, 2008
November 3, 2008 10:58:28 PM
Also Known As:
WORM_KERBOT.A [Trend], Win32/Kerbot.A [Computer Associates]
Trojan, Worm
Infection Length:
Systems Affected:
CVE References:
The worm may arrive on to the compromised computer through network vulnerabilities or through file sharing networks.

If the worm is spread through network vulnerabilities, it may arrive as the following files:
  • 6767.exe
  • KernekDbg.exe

If the worm is spread through Peer to Peer file sharing, it may arrive as the following files:
  • keygens.exe
  • iedvv.exe

Once executed, the worm attempts to lower security settings by modifying the following registry entries:
  • HKEY_LOCAL_MACHINE\SOFTWARE\360Safe\safemon\"UDiskAccess" = "0"
  • HKEY_LOCAL_MACHINE\SOFTWARE\360Safe\safemon\"ExecAccess" = "0"
  • HKEY_LOCAL_MACHINE\SOFTWARE\360Safe\safemon\"IEProtAccess" = "0"
  • HKEY_LOCAL_MACHINE\SOFTWARE\360Safe\safemon\"LeakAccess" = "0"
  • HKEY_LOCAL_MACHINE\SOFTWARE\360Safe\safemon\"MonAccess" = "0"
  • HKEY_LOCAL_MACHINE\SOFTWARE\360Safe\safemon\"SiteAccess" = "0"

It creates some of the following files and sets the file attributes as hidden. It also changes the timestamp of these files to the legitimate Windows WINLOGON.EXE timestamp:
  • %System%\[FILE NAME].sys
  • %System%\[FILE NAME].zip
  • %System%\[FILE NAME].exe
  • %System%\[FILE NAME].dll
  • %System%\[FILE NAME].ocx
  • %System%\[FILE NAME].ini

    [FILE NAME] is a file name chosen by the remote attacker and reportedly includes the following observed file names:
  • compbatc.sys
  • compbatc.zip
  • compbatc.exe
  • vvebc1nt.sys
  • vvebc1nt.zip
  • vvebc1nt.exe

Next, it creates the following registry subkeys to register some files as Windows services and to run code in Kernel mode:
  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\compbatc
  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\compbatcDrv
  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\[8 NUMBERS]

It attempts to end the following processes, if found, using the newly registered services:
  • safeboxtray.exe
  • 360tray.exe
  • iparmor.exe
  • RSTray.exe
  • USBSAFE.exe
  • 360rpt.exe

It attempts to delete the following registry entries to prevent automatic execution of certain programs when Windows starts:
  • HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run\"360Safetray"
  • HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run\"360Safebox"
  • HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run\"360Antiarp"
  • HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run\"runeip"
  • HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run\"Iparmor"

It deletes the following registry subkeys to prevent the compromised computer from restarting in Safe Mode:
  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\SafeBoot\Network
  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\SafeBoot\Minimal

Note: Deletion of the subkeys reportedly may display a Blue Screen error.

It may contact the following remote location to download commands from the attacker:

The worm is then able to perform the following actions:
  • Update itself
  • Download and execute additional malicious files
  • Download files or archives to be spread over P2P networks
  • Participate in distributed denial of service attacks against remote sites using a UDP, TCP, SYN, or HTTP flood

It reports its status and information about the compromised computer to the following Web site:

At the time of writing, the worm reportedly downloads the following files:
  • [http://]zz.ushealthmart.com/67.[REMOVED] (Bloodhound.Exploit.212)
  • [http://]st.ushealthmart.com/webc[REMOVED] (W32.Kernelbot.A)

The file 67.exe is a copy of the exploit code for the following remote vulnerability and is used to spread the worm over the local network:
Microsoft Windows Server Service RPC Handling Remote Code Execution Vulnerability (BID 31874)

The worm will download and run the following file on successfully attacked and exploited computers :
[http://]zz.ushealthmart.com/download/6767[REMOVED] (W32.Kernelbot.A)

The worm may use the webcc.exe file, if downloaded, to contact the following remote locations:
  • [http://][REMOVED]
  • [http://][REMOVED]

The worm may download or create the following files which contain custom Windows scripts to be executed on the compromised computer:

It has been observed that the worm can download and install the eMule P2P client program on the compromised computer. The eMule software is downloaded as a unique package from the following remote locations:
  • [http://]freegoogla.vicp.net/download/Loade[REMOVED] (W32.Kernelbot.A)
  • [http://]freegoogla.vicp.net/download/Demo[REMOVED] (W32.Kernelbot.A, RAR archive)
  • [http://]freegoogla.vicp.net/download/em_set[REMOVED] (W32.Kernelbot.A, sefl-extracting RAR)

When the eMule client is successfully downloaded and installed on the compromised computer, the worm tries to spread across P2P network by sharing a misleading movie file which is a copy of the worm.

It adds the following lines of text to the hosts file to prevent access to various domains:
  • 360.cn
  • alert.rising.com.cn
  • baike.360.cn
  • bbs.360.cn
  • bbs.360safe.com
  • bbs.cpcw.com
  • bbs.dswlab.com
  • bbs.duba.net
  • bbs.ikaka.com
  • bbs.janmeng.com
  • bbs.kafan.cn
  • bbs.kaspersky.com.cn
  • bbs.mcafeefans.com
  • bbs.sucop.com
  • bbs.trendmicro.com.cn
  • buy.rising.com.cn
  • center.rising.com.cn
  • cn.mcafee.com
  • cn.trendmicro.com
  • csc.rising.com.cn
  • dnl-cd1.kaspersky-labs.com
  • dnl-cd10.kaspersky-labs.com
  • dnl-cd11.kaspersky-labs.com
  • dnl-cd12.kaspersky-labs.com
  • dnl-cd13.kaspersky-labs.com
  • dnl-cd14.kaspersky-labs.com
  • dnl-cd2.kaspersky-labs.com
  • dnl-cd3.kaspersky-labs.com
  • dnl-cd4.kaspersky-labs.com
  • dnl-cd5.kaspersky-labs.com
  • dnl-cd6.kaspersky-labs.com
  • dnl-cd7.kaspersky-labs.com
  • dnl-cd8.kaspersky-labs.com
  • dnl-cd9.kaspersky-labs.com
  • dnl-cn1.kaspersky-labs.com
  • dnl-cn10.kaspersky-labs.com
  • dnl-cn11.kaspersky-labs.com
  • dnl-cn12.kaspersky-labs.com
  • dnl-cn13.kaspersky-labs.com
  • dnl-cn14.kaspersky-labs.com
  • dnl-cn15.kaspersky-labs.com
  • dnl-cn2.kaspersky-labs.com
  • dnl-cn3.kaspersky-labs.com
  • dnl-cn4.kaspersky-labs.com
  • dnl-cn5.kaspersky-labs.com
  • dnl-cn6.kaspersky-labs.com
  • dnl-cn7.kaspersky-labs.com
  • dnl-cn8.kaspersky-labs.com
  • dnl-cn9.kaspersky-labs.com
  • dnl-eu1.kaspersky-labs.com
  • dnl-eu10.kaspersky-labs.com
  • dnl-eu11.kaspersky-labs.com
  • dnl-eu12.kaspersky-labs.com
  • dnl-eu13.kaspersky-labs.com
  • dnl-eu14.kaspersky-labs.com
  • dnl-eu15.kaspersky-labs.com
  • dnl-eu2.kaspersky-labs.com
  • dnl-eu3.kaspersky-labs.com
  • dnl-eu4.kaspersky-labs.com
  • dnl-eu5.kaspersky-labs.com
  • dnl-eu6.kaspersky-labs.com
  • dnl-eu7.kaspersky-labs.com
  • dnl-eu8.kaspersky-labs.com
  • dnl-eu9.kaspersky-labs.com
  • dnl-jp1.kaspersky-labs.com
  • dnl-jp10.kaspersky-labs.com
  • dnl-jp11.kaspersky-labs.com
  • dnl-jp12.kaspersky-labs.com
  • dnl-jp13.kaspersky-labs.com
  • dnl-jp14.kaspersky-labs.com
  • dnl-jp15.kaspersky-labs.com
  • dnl-jp2.kaspersky-labs.com
  • dnl-jp3.kaspersky-labs.com
  • dnl-jp4.kaspersky-labs.com
  • dnl-jp5.kaspersky-labs.com
  • dnl-jp6.kaspersky-labs.com
  • dnl-jp7.kaspersky-labs.com
  • dnl-jp8.kaspersky-labs.com
  • dnl-jp9.kaspersky-labs.com
  • dnl-kr1.kaspersky-labs.com
  • dnl-kr10.kaspersky-labs.com
  • dnl-kr11.kaspersky-labs.com
  • dnl-kr12.kaspersky-labs.com
  • dnl-kr13.kaspersky-labs.com
  • dnl-kr14.kaspersky-labs.com
  • dnl-kr15.kaspersky-labs.com
  • dnl-kr2.kaspersky-labs.com
  • dnl-kr3.kaspersky-labs.com
  • dnl-kr4.kaspersky-labs.com
  • dnl-kr5.kaspersky-labs.com
  • dnl-kr6.kaspersky-labs.com
  • dnl-kr7.kaspersky-labs.com
  • dnl-kr8.kaspersky-labs.com
  • dnl-kr9.kaspersky-labs.com
  • dnl-ru1.kaspersky-labs.com
  • dnl-ru10.kaspersky-labs.com
  • dnl-ru11.kaspersky-labs.com
  • dnl-ru12.kaspersky-labs.com
  • dnl-ru13.kaspersky-labs.com
  • dnl-ru14.kaspersky-labs.com
  • dnl-ru15.kaspersky-labs.com
  • dnl-ru2.kaspersky-labs.com
  • dnl-ru3.kaspersky-labs.com
  • dnl-ru4.kaspersky-labs.com
  • dnl-ru5.kaspersky-labs.com
  • dnl-ru6.kaspersky-labs.com
  • dnl-ru7.kaspersky-labs.com
  • dnl-ru8.kaspersky-labs.com
  • dnl-ru9.kaspersky-labs.com
  • dnl-us1.kaspersky-labs.com
  • dnl-us10.kaspersky-labs.com
  • dnl-us11.kaspersky-labs.com
  • dnl-us12.kaspersky-labs.com
  • dnl-us13.kaspersky-labs.com
  • dnl-us14.kaspersky-labs.com
  • dnl-us15.kaspersky-labs.com
  • dnl-us2.kaspersky-labs.com
  • dnl-us3.kaspersky-labs.com
  • dnl-us4.kaspersky-labs.com
  • dnl-us5.kaspersky-labs.com
  • dnl-us6.kaspersky-labs.com
  • dnl-us7.kaspersky-labs.com
  • dnl-us8.kaspersky-labs.com
  • dnl-us9.kaspersky-labs.com
  • download.rising.com.cn
  • dswlab.com
  • file.ikaka.com
  • forum.ikaka.com
  • forum.jiangmin.com
  • fw.rising.com.cn
  • go.rising.com.cn
  • help.rising.com.cn
  • kaba.360.cn
  • kpfans.com
  • mcafeefans.com
  • online.jiangmin.com
  • online.rising.com.cn
  • security.symantec.com
  • shadu.baidu.com
  • shadu.duba.net
  • sos.rising.com.cn
  • sucop.com
  • tool.ikaka.com
  • up.duba.net
  • update.ikaka.com
  • update.rising.com.cn
  • www.360.cn
  • www.360Safe.com
  • www.ahn.com.cn
  • www.dswlab.com
  • www.ikaka.com
  • www.kaspersky.com
  • www.kaspersky.com.cn
  • www.kpfans.com
  • www.kztechs.com
  • www.mcafee.com
  • www.pcav.cn
  • www.rising.com.cn
  • www.shudoo.com
  • www.sucop.com
  • www.trendmicro.com.cn
  • www.vrv.com.cn
  • zhidao.ikaka.com


Symantec Security Response encourages all users and administrators to adhere to the following basic security "best practices":

  • Use a firewall to block all incoming connections from the Internet to services that should not be publicly available. By default, you should deny all incoming connections and only allow services you explicitly want to offer to the outside world.
  • Enforce a password policy. Complex passwords make it difficult to crack password files on compromised computers. This helps to prevent or limit damage when a computer is compromised.
  • Ensure that programs and users of the computer use the lowest level of privileges necessary to complete a task. When prompted for a root or UAC password, ensure that the program asking for administration-level access is a legitimate application.
  • Disable AutoPlay to prevent the automatic launching of executable files on network and removable drives, and disconnect the drives when not required. If write access is not required, enable read-only mode if the option is available.
  • Turn off file sharing if not needed. If file sharing is required, use ACLs and password protection to limit access. Disable anonymous access to shared folders. Grant access only to user accounts with strong passwords to folders that must be shared.
  • Turn off and remove unnecessary services. By default, many operating systems install auxiliary services that are not critical. These services are avenues of attack. If they are removed, threats have less avenues of attack.
  • If a threat exploits one or more network services, disable, or block access to, those services until a patch is applied.
  • Always keep your patch levels up-to-date, especially on computers that host public services and are accessible through the firewall, such as HTTP, FTP, mail, and DNS services.
  • Configure your email server to block or remove email that contains file attachments that are commonly used to spread threats, such as .vbs, .bat, .exe, .pif and .scr files.
  • Isolate compromised computers quickly to prevent threats from spreading further. Perform a forensic analysis and restore the computers using trusted media.
  • Train employees not to open attachments unless they are expecting them. Also, do not execute software that is downloaded from the Internet unless it has been scanned for viruses. Simply visiting a compromised Web site can cause infection if certain browser vulnerabilities are not patched.
  • If Bluetooth is not required for mobile devices, it should be turned off. If you require its use, ensure that the device's visibility is set to "Hidden" so that it cannot be scanned by other Bluetooth devices. If device pairing must be used, ensure that all devices are set to "Unauthorized", requiring authorization for each connection request. Do not accept applications that are unsigned or sent from unknown sources.
  • For further information on the terms used in this document, please refer to the Security Response glossary.
Writeup By: Elia Florio
Summary| Technical Details| Removal

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