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Symantec.com > Security Response > Threats and Risks > Trojan.Tooso.K
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Trojan.Tooso.K

Risk Level 2: Low

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Discovered: August 8, 2005
Updated: February 13, 2007 12:43:10 PM
Also Known As: TROJ_BAGLE.AA [Trend Micro]
Type: Trojan Horse
Systems Affected: Windows 2000, Windows 95, Windows 98, Windows Me, Windows NT, Windows Server 2003, Windows XP


This Trojan may arrive in an email with a .zip file attachment. The attachment may contain the file foto_bs363.exe.

When Trojan.Tooso.K is executed, it performs the following actions:
  1. Executes the following program:

    mspaint.exe.

  2. Copies itself as %System%\winshost.exe.

    Note: %System% is a variable that refers to the System folder. By default this is C:\Windows\System (Windows 95/98/Me), C:\Winnt\System32 (Windows NT/2000), or C:\Windows\System32 (Windows XP).

  3. Drops the following file:

    %System%\wiwshost.exe

  4. Adds the value:

    "winshost.exe" = "%System%\winshost.exe"

    to the registry subkeys:

    HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run

    so that it runs every time Windows starts.

  5. Adds the value:

    "Start" = "4"

    to the registry subkey:

    HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\SharedAccess

    so that it disables the Shared Access service in Windows 2000/XP.

  6. Adds the value:

    "Start" = "4"

    to the registry subkey:

    HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\wuauserv

    so that it disables Automatic Updates.

  7. Adds the value:

    "Start" = "4"

    to the registry subkey:

    HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Alerter

    so that it disables the Alerter service.

  8. Injects wiwshost.exe into the explorer.exe process. All of the Trojan's subsequent actions will appear to be performed by explorer.exe.

  9. Stops services with the following names:

    • AVExch32Service
    • AVPCC
    • AVUPDService
    • Ahnlab task Scheduler
    • AlertManger
    • AvgCore
    • AvgFsh
    • AvgServ
    • AvxIni
    • BackWeb Client - 7681197
    • BlackICE
    • CAISafe
    • DefWatch
    • F-Secure Gatekeeper Handler Starter
    • FSDFWD
    • FSMA
    • KAVMonitorService
    • KLBLMain
    • MCVSRte
    • McAfee Firewall
    • McAfeeFramework
    • McShield
    • McTaskManager
    • MonSvcNT
    • NISSERV
    • NISUM
    • NOD32ControlCenter
    • NOD32Service
    • NPFMntor
    • NProtectService
    • NSCTOP
    • NVCScheduler
    • NWService
    • Network Associates Log Service
    • Norman NJeeves
    • Norman ZANDA
    • Norton Antivirus Server
    • Outbreak Manager
    • Outpost Firewall
    • OutpostFirewall
    • PASSRV
    • PAVFNSVR
    • PAVSRV
    • PCCPFW
    • PREVSRV
    • PSIMSVC
    • PavPrSrv
    • PavProt
    • Pavkre
    • PersFW
    • SAVFMSE
    • SAVScan
    • SBService
    • SNDSrvc
    • SPBBCSvc
    • SWEEPSRV.SYS
    • SharedAccess
    • SmcService
    • SweepNet
    • Symantec AntiVirus Client
    • Symantec Core LC
    • Tmntsrv
    • V3MonNT
    • V3MonSvc
    • VexiraAntivirus
    • VisNetic AntiVirus Plug-in
    • XCOMM
    • alerter
    • avg7alrt
    • avg7updsvc
    • avpcc
    • awhost32
    • backweb client - 4476822
    • backweb client-4476822
    • ccEvtMgr
    • ccPwdSvc
    • ccSetMgr
    • ccSetMgr.exe
    • dvpapi
    • dvpinit
    • fsbwsys
    • fsdfwd
    • kavsvc
    • mcupdmgr.exe
    • navapsvc
    • nvcoas
    • nwclntc
    • nwclntd
    • nwclnte
    • nwclntf
    • nwclntg
    • nwclnth
    • ravmon8
    • schscnt
    • sharedaccess
    • vsmon
    • wuauserv

  10. Attempts to delete the following registry subkeys:

    HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion
    \Run\Symantec NetDriver Monitor
    HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion
    \Run\ccApp
    HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion
    \Run\NAV CfgWiz
    HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion
    \Run\SSC_UserPrompt
    HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion
    \Run\McAfee Guardian
    HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion
    \Run\APVXDWIN
    HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion
    \Run\KAV50
    HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion
    \Run\avg7_cc
    HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion
    \Run\avg7_emc
    HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion
    \Run\Zone Labs Client
    HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion
    \Run\McAfee.InstantUpdate.Monitor

    to disable the automatic startup of certain security-related programs.
  11. Attempts to delete the following registry subkeys:

    HKEY_LOCAL_MACHINE\SOFTWARE\Symantec
    HKEY_LOCAL_MACHINE\SOFTWARE\McAfee
    HKEY_LOCAL_MACHINE\SOFTWARE\KasperskyLab
    HKEY_LOCAL_MACHINE\SOFTWARE\Agnitum
    HKEY_LOCAL_MACHINE\SOFTWARE\Panda Software
    HKEY_LOCAL_MACHINE\SOFTWARE\Zone Labs

    to disable certain security-related programs.
  12. Attempts to delete all instances of files with the following names from all fixed drives:

    • AUPD1ATE.EXE
    • AUPDATE.EXE
    • Av1synmgr.exe
    • Avc1onsol.exe
    • Avconsol.exe
    • Avsynmgr.exe
    • C1CSETMGR.EXE
    • CC1EVTMGR.EXE
    • CCEVTMGR.EXE
    • CCSETMGR.EXE
    • CM1Grdian.exe
    • CMGrdian.exe
    • K2A2V.exe
    • KAV.exe
    • LUAL1L.EXE
    • LUALL.EXE
    • LUI1NSDLL.DLL
    • LUINSDLL.DLL
    • Luup1date.exe
    • Luupdate.exe
    • Mcsh1ield.exe
    • Mcshield.exe
    • NAV1APSVC.EXE
    • NAVAPSVC.EXE
    • NPFM1NTOR.EXE
    • NPFMNTOR.EXE
    • RuLa1unch.exe
    • RuLaunch.exe
    • SND1Srvc.exe
    • SNDSrvc.exe
    • SP1BBCSvc.exe
    • SPBBCSvc.exe
    • Up222Date.exe
    • Up2Date.exe
    • Vs1Stat.exe
    • VsStat.exe
    • Vshw1in32.exe
    • Vshwin32.exe
    • a5v.dll
    • av.dll
    • avg23emc.exe
    • avgc3c.exe
    • avgcc.exe
    • avgemc.exe
    • c6a5fix.exe
    • cafix.exe
    • cc1l30.dll
    • ccA1pp.exe
    • ccApp.exe
    • ccl30.dll
    • ccv1rtrst.dll
    • ccvrtrst.dll
    • is5a6fe.exe
    • isafe.exe
    • kav12mm.exe
    • kavmm.exe
    • outp1ost.exe
    • outpost.exe
    • s1ymlcsvc.exe
    • symlcsvc.exe
    • ve6tre5dir.dll
    • vetredir.dll
    • vs6va5ult.dll
    • vsvault.dll
    • zatu6tor.exe
    • zatutor.exe
    • zl5avscan.dll
    • zlavscan.dll
    • zlcli6ent.exe
    • zlclient.exe
    • zo3nealarm.exe
    • zonealarm.exe

  13. Attempts to stop the following services:

    • SharedAccess
    • wscsvc

  14. Attempts to end processes with the following names:

    • ATUPDATER.EXE
    • AUPDATE.EXE
    • AUTODOWN.EXE
    • AUTOTRACE.EXE
    • AUTOUPDATE.EXE
    • AVPUPD.ExE
    • AVWUPD32.EXE
    • AVXQUAR.EXE
    • CFIAUDIT.EXE
    • DRWEBUPW.EXE
    • ESCANH95.EXE
    • ESCANHNT.EXE
    • FIREWALL.EXE
    • ICSSUPPNT.EXE
    • ICSUPP95.EXE
    • LUALL.EXE
    • MCUPDATE.EXE
    • NUPGRADE.EXE
    • OUTPOST.ExE
    • UPDATE.Exe
    • UPGRADER.EXE

  15. Attempts to download files from the following URLs in the sequence given. At the time of writing, the files were not available:

    • [http://]www.21ebuild.com/[REMOVED]/osa4.gif
    • [http://]www.51.net/[REMOVED]/osa4.gif
    • [http://]www.acsohio.com/[REMOVED]/osa4.gif
    • [http://]www.agria.hu/[REMOVED]/osa4.gif
    • [http://]www.andi.com.vn/[REMOVED]/osa4.gif
    • [http://]www.angham.de/[REMOVED]/osa4.gif
    • [http://]www.ascolfibras.com/[REMOVED]/osa4.gif
    • [http://]www.automobilonline.de/[REMOVED]/osa4.gif
    • [http://]www.bangyan.cn/[REMOVED]/osa4.gif
    • [http://]www.beall-cpa.com/[REMOVED]/osa4.gif
    • [http://]www.bolz.at/[REMOVED]/osa4.gif
    • [http://]www.bs-security.de/[REMOVED]/osa4.gif
    • [http://]www.centrovestecasa.it/[REMOVED]/osa4.gif
    • [http://]www.checkonemedia.nl/[REMOVED]/osa4.gif
    • [http://]www.contentproject.com/[REMOVED]/osa4.gif
    • [http://]www.cz-wanjia.com/[REMOVED]/osa4.gif
    • [http://]www.czwanqing.com/[REMOVED]/osa4.gif
    • [http://]www.czzm.com/[REMOVED]/osa4.gif
    • [http://]www.datanet.huwww.datanet.hu/[REMOVED]/osa4.gif
    • [http://]www.designgong.org/[REMOVED]/osa4.gif
    • [http://]www.dgy.com.cn/[REMOVED]/osa4.gif
    • [http://]www.die-fliesen.de/[REMOVED]/osa4.gif
    • [http://]www.discoteka-funfactory.com/[REMOVED]/osa4.gif
    • [http://]www.dom-invest.com.pl/[REMOVED]/osa4.gif
    • [http://]www.eagle.com.cn/[REMOVED]/osa4.gif
    • [http://]www.eagleclub.com.cn/[REMOVED]/osa4.gif
    • [http://]www.ehc.hu/[REMOVED]/osa4.gif
    • [http://]www.elvis-presley.ch/[REMOVED]/osa4.gif
    • [http://]www.engelhardtgmbh.de/[REMOVED]/osa4.gif
    • [http://]www.externet.hu/[REMOVED]/osa4.gif
    • [http://]www.fahrschule-herb.de/[REMOVED]/osa4.gif
    • [http://]www.fahrschule-lesser.de/[REMOVED]/osa4.gif
    • [http://]www.fermegaroy.com/[REMOVED]/osa4.gif
    • [http://]www.festivalteatrooccidente.com/[REMOVED]/osa4.gif
    • [http://]www.formholz.at/[REMOVED]/osa4.gif
    • [http://]www.fotomax.fi/[REMOVED]/osa4.gif
    • [http://]www.gemtrox.com.tw/[REMOVED]/osa4.gif
    • [http://]www.gepeters.org/[REMOVED]/osa4.gif
    • [http://]www.gimex-messzeuge.de/[REMOVED]/osa4.gif
    • [http://]www.gomyhome.com.tw/[REMOVED]/osa4.gif
    • [http://]www.gymzn.cz/[REMOVED]/osa4.gif
    • [http://]www.hondenservice.be/[REMOVED]/osa4.gif
    • [http://]www.idaf.de/[REMOVED]/osa4.gif
    • [http://]www.idcs.be/[REMOVED]/osa4.gif
    • [http://]www.ider.cl/[REMOVED]/osa4.gif
    • [http://]www.inside-tgweb.de/[REMOVED]/osa4.gif
    • [http://]www.izoli.sk/[REMOVED]/osa4.gif
    • [http://]www.jcm-american.com/[REMOVED]/osa4.gif
    • [http://]www.jeoushinn.com/[REMOVED]/osa4.gif
    • [http://]www.jingjuok.com/[REMOVED]/osa4.gif
    • [http://]www.jue-bo.com/[REMOVED]/osa4.gif
    • [http://]www.kingsley.ch/[REMOVED]/osa4.gif
    • [http://]www.marketvw.com/[REMOVED]/osa4.gif
    • [http://]www.megaserve.net/[REMOVED]/osa4.gif
    • [http://]www.mild.at/[REMOVED]/osa4.gif
    • [http://]www.niko.de/[REMOVED]/osa4.gif
    • [http://]www.nikogmbh.com/[REMOVED]/osa4.gif
    • [http://]www.olva.com.pe/[REMOVED]/osa4.gif
    • [http://]www.on24.ee/[REMOVED]/osa4.gif
    • [http://]www.onlink.net/[REMOVED]/osa4.gif
    • [http://]www.ppm-alliance.de/[REMOVED]/osa4.gif
    • [http://]www.presley.ch/[REMOVED]/osa4.gif
    • [http://]www.renegaderc.com/[REMOVED]/osa4.gif
    • [http://]www.replayu.com/[REMOVED]/osa4.gif
    • [http://]www.sachsenbuecher.de/[REMOVED]/osa4.gif
    • [http://]www.sanjinyuan.com/[REMOVED]/osa4.gif
    • [http://]www.scvanravenswaaij.nl/[REMOVED]/osa4.gif
    • [http://]www.slovanet.sk/[REMOVED]/osa4.gif
    • [http://]www.snsphoto.com/[REMOVED]/osa4.gif
    • [http://]www.societaet.de/[REMOVED]/osa4.gif
    • [http://]www.soeco.org/[REMOVED]/osa4.gif
    • [http://]www.softmajor.ru/[REMOVED]/osa4.gif
    • [http://]www.solt3.org/[REMOVED]/osa4.gif
    • [http://]www.spacium.biz/[REMOVED]/osa4.gif
    • [http://]www.speedcom.home.pl/[REMOVED]/osa4.gif
    • [http://]www.spirit-in-steel.at/[REMOVED]/osa4.gif
    • [http://]www.spoden.de/[REMOVED]/osa4.gif
    • [http://]www.sportnf.com/[REMOVED]/osa4.gif
    • [http://]www.spy.az/[REMOVED]/osa4.gif
    • [http://]www.sqnsolutions.com/[REMOVED]/osa4.gif
    • [http://]www.st-paulus-bonn.dehtdocs/[REMOVED]/osa4.gif
    • [http://]www.stbs.com.hk/[REMOVED]/osa4.gif
    • [http://]www.steripharm.com/[REMOVED]/osa4.gif
    • [http://]www.students.stir.ac.uk/[REMOVED]/osa3.gif
    • [http://]www.subsplanet.com/[REMOVED]/osa4.gif
    • [http://]www.sungodbio.com/[REMOVED]/osa4.gif
    • [http://]www.superbetcs.com/[REMOVED]/osa4.gif
    • [http://]www.sweb.cz/[REMOVED]/osa4.gif
    • [http://]www.sydolo.com/[REMOVED]/osa4.gif
    • [http://]www.szdiheng.com/[REMOVED]/osa4.gif
    • [http://]www.tcicampus.net/[REMOVED]/osa4.gif
    • [http://]www.techni.com.cn/[REMOVED]/osa4.gif
    • [http://]www.tg-sandhausen-basketball.de/[REMOVED]/osa4.gif
    • [http://]www.th-mutan.com/[REMOVED]/osa4.gif
    • [http://]www.thaifast.com/[REMOVED]/osa4.gif
    • [http://]www.thaiventure.com/[REMOVED]/osa4.gif
    • [http://]www.thefunkiest.com/[REMOVED]/osa4.gif
    • [http://]www.thenextstep.tv/[REMOVED]/osa4.gif
    • [http://]www.thetexasoutfitter.com/[REMOVED]/osa4.gif
    • [http://]www.tmhcsd1987.friko.pl/[REMOVED]/osa4.gif
    • [http://]www.toussain.be/[REMOVED]/osa4.gif
    • [http://]www.trago.com.pt/[REMOVED]/osa4.gif
    • [http://]www.travelourway.com/[REMOVED]/osa4.gif
    • [http://]www.trgd.dobrcz.pl/[REMOVED]/osa4.gif
    • [http://]www.triapex.cz/[REMOVED]/osa4.gif
    • [http://]www.triptonic.ch/[REMOVED]/osa4.gif
    • [http://]www.tv-marina.com/[REMOVED]/osa4.gif
    • [http://]www.udc-cassinadepecchi.it/[REMOVED]/osa4.gif
    • [http://]www.universe.sk/[REMOVED]/osa4.gif
    • [http://]www.uspowerchair.com/[REMOVED]/osa4.gif
    • [http://]www.uw.hu/[REMOVED]/osa4.gif
    • [http://]www.vercruyssenelektro.be/[REMOVED]/osa4.gif
    • [http://]www.vet24h.com/[REMOVED]/osa4.gif
    • [http://]www.vinimeloni.com/[REMOVED]/osa4.gif
    • [http://]www.vnn.vn/[REMOVED]/osa4.gif
    • [http://]www.vnrvjiet.ac.in/[REMOVED]/osa4.gif
    • [http://]www.vote2fateh.com/[REMOVED]/osa4.gif
    • [http://]www.vw.press-bank.pl/[REMOVED]/osa4.gif
    • [http://]www.wamba.asn.au/[REMOVED]/osa4.gif
    • [http://]www.wdlp.co.za/[REMOVED]/osa4.gif
    • [http://]www.welchcorp.com/[REMOVED]/osa4.gif
    • [http://]www.wesartproductions.com/[REMOVED]/osa4.gif
    • [http://]www.wilsonscountry.com/[REMOVED]/osa4.gif
    • [http://]www.windstar.pl/[REMOVED]/osa4.gif
    • [http://]www.wise-industries.com/[REMOVED]/osa4.gif
    • [http://]www.witold.pl/[REMOVED]/osa4.gif
    • [http://]www.wombband.com/[REMOVED]/osa4.gif
    • [http://]www.x-treme.cz/[REMOVED]/osa4.gif
    • [http://]www.xiantong.net/[REMOVED]/osa4.gif
    • [http://]www.xmpie.com/[REMOVED]/osa4.gif
    • [http://]www.xmtd.com/[REMOVED]/osa4.gif
    • [http://]www.xojc.com/[REMOVED]/osa4.gif
    • [http://]www.yannick-spruyt.be/[REMOVED]/osa4.gif
    • [http://]www.yayadownload.com/[REMOVED]/osa4.gif
    • [http://]www.yesterdays.co.za/[REMOVED]/osa4.gif
    • [http://]www.yshkj.com/[REMOVED]/osa4.gif
    • [http://]www.zakazcd.dp.ua/[REMOVED]/osa4.gif
    • [http://]www.zenesoftware.com/[REMOVED]/osa4.gif
    • [http://]www.zentek.co.za/[REMOVED]/osa4.gif
    • [http://]www.zorbas.az/[REMOVED]/osa4.gif
    • [http://]www.zsbersala.edu.sk/[REMOVED]/osa4.gif

  16. Overwrites the infected computer's hosts file with the following text:

    127.0.0.1 localhost


Recommendations

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: Jeong Mun
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