Threat Encyclopedia

Selected viruses, spyware, and other threats: sorted alphabetically

Trojandownloader.Small.ZL

This trojan is a typical Downloader Trojan. The size is 37888 bytes and the trojan is runtime compressed / protected by PEX, an executable file compressor.

Note: In the following text, %windir% denotes Windows directory (e.g. C:\WINDOWS) and %system% denotes Windows System directory (e.g. C:\WINDOWS\SYSTEM32) as they differ on various versions of Microsoft Windows.

Installation and Autostart Techniques

Upon execution the trojan drops components into the Windows System folder as "wiwshost.exe" (18944 bytes) and "winshost.exe" (9728 bytes).

Note: wiwshost.exe is a DLL file which is injected into Explorer.exe process and represents the main downloading component. This file is not packed.

The trojan adds the following registry keys to the registry to make sure that it runs every time windows is started:

HKLM\Software\Microsoft\Windows\CurrentVersion\Run
"winshost.exe" = "%SYSTEM%\winshost.exe"

HKCU\Software\Microsoft\Windows\CurrentVersion\Run
"winshost.exe" = "%SYSTEM%\winshost.exe"

If the trojan finds one of the following values

Run,Symantec NetDriver Monitor
Run,ccApp
Run,NAV CfgWiz
Run,SSC_UserPrompt
Run,McAfee Guardian
Run,McAfee.InstantUpdate.Monitor
Run,APVXDWIN
Run,KAV50
Run,avg7_cc
Run,avg7_emc
Run,Zone Labs Client

at HKLM\Software\Microsoft\Windows\CurrentVersion\Run and / or

Symantec
McAfee
KasperskyLab
Agnitum
Panda Software
Zone Labs

at HKLM\SOFTWARE, then the worm removes these startup values in it's own thread that watches for these values.

The malicious process WIWSHOST is now running 'cloaked' inside the Explorer Task.
It overwrites the existing %system32%\Drivers\etc\hosts file with the following data

127.0.0.1 localhost
127.0.0.1 ad.doubleclick.net
127.0.0.1 ad.fastclick.net
127.0.0.1 ads.fastclick.net
127.0.0.1 ar.atwola.com
127.0.0.1 atdmt.com
127.0.0.1 avp.ch
127.0.0.1 avp.com
127.0.0.1 avp.ru
127.0.0.1 awaps.net
127.0.0.1 banner.fastclick.net
127.0.0.1 banners.fastclick.net
127.0.0.1 ca.com
127.0.0.1 click.atdmt.com
127.0.0.1 clicks.atdmt.com
127.0.0.1 dispatch.mcafee.com
127.0.0.1 download.mcafee.com
127.0.0.1 download.microsoft.com
127.0.0.1 downloads.microsoft.com
127.0.0.1 engine.awaps.net
127.0.0.1 fastclick.net
127.0.0.1 f-secure.com
127.0.0.1 ftp.f-secure.com
127.0.0.1 ftp.sophos.com
127.0.0.1 go.microsoft.com
127.0.0.1 liveupdate.symantec.com
127.0.0.1 mast.mcafee.com
127.0.0.1 mcafee.com
127.0.0.1 media.fastclick.net
127.0.0.1 msdn.microsoft.com
127.0.0.1 my-etrust.com
127.0.0.1 nai.com
127.0.0.1 networkassociates.com
127.0.0.1 office.microsoft.com
127.0.0.1 phx.corporate-ir.net
127.0.0.1 secure.nai.com
127.0.0.1 securityresponse.symantec.com
127.0.0.1 service1.symantec.com
127.0.0.1 sophos.com
127.0.0.1 spd.atdmt.com
127.0.0.1 support.microsoft.com
127.0.0.1 symantec.com
127.0.0.1 update.symantec.com
127.0.0.1 updates.symantec.com
127.0.0.1 us.mcafee.com
127.0.0.1 vil.nai.com
127.0.0.1 viruslist.ru
127.0.0.1 windowsupdate.microsoft.com
127.0.0.1 www.avp.ch
127.0.0.1 www.avp.com
127.0.0.1 www.avp.ru
127.0.0.1 www.awaps.net
127.0.0.1 www.ca.com
127.0.0.1 www.fastclick.net
127.0.0.1 www.f-secure.com
127.0.0.1 www.kaspersky.ru
127.0.0.1 www.mcafee.com
127.0.0.1 www.my-etrust.com
127.0.0.1 www.nai.com
127.0.0.1 www.networkassociates.com
127.0.0.1 www.sophos.com
127.0.0.1 www.symantec.com
127.0.0.1 www.trendmicro.com
127.0.0.1 www.viruslist.ru
127.0.0.1 ftp://ftp.kasperskylab.ru/updates/
127.0.0.1 ftp://ftp.avp.ch/updates/
127.0.0.1 http://www.kaspersky.ru/updates/
127.0.0.1 http://updates1.kaspersky-labs.com/updates/
127.0.0.1 http://updates3.kaspersky-labs.com/updates/
127.0.0.1 http://updates4.kaspersky-labs.com/updates/
127.0.0.1 http://updates2.kaspersky-labs.com/updates/
127.0.0.1 http://updates5.kaspersky-labs.com/updates/
127.0.0.1 http://downloads1.kaspersky-labs.com/updates/
127.0.0.1 http://www.kaspersky-labs.com/updates/
127.0.0.1 ftp://updates3.kaspersky-labs.com/updates/
127.0.0.1 ftp://downloads1.kaspersky-labs.com/updates/
127.0.0.1 www3.ca.com
127.0.0.1 ids.kaspersky-labs.com
127.0.0.1 downloads2.kaspersky-labs.com
127.0.0.1 downloads1.kaspersky-labs.com
127.0.0.1 downloads3.kaspersky-labs.com
127.0.0.1 downloads4.kaspersky-labs.com
127.0.0.1 liveupdate.symantecliveupdate.com
127.0.0.1 liveupdate.symantec.com
127.0.0.1 update.symantec.com
127.0.0.1 download.mcafee.com
127.0.0.1 www.symantec.com
127.0.0.1 securityresponse.symantec.com
127.0.0.1 symantec.com
127.0.0.1 www.sophos.com
127.0.0.1 sophos.com
127.0.0.1 www.mcafee.com
127.0.0.1 mcafee.com
127.0.0.1 liveupdate.symantecliveupdate.com
127.0.0.1 www.viruslist.com
127.0.0.1 viruslist.com
127.0.0.1 f-secure.com
127.0.0.1 www.f-secure.com
127.0.0.1 kaspersky.com
127.0.0.1 kaspersky-labs.com
127.0.0.1 www.avp.com
127.0.0.1 www.kaspersky.com
127.0.0.1 avp.com
127.0.0.1 www.networkassociates.com
127.0.0.1 networkassociates.com
127.0.0.1 www.ca.com
127.0.0.1 ca.com
127.0.0.1 mast.mcafee.com
127.0.0.1 my-etrust.com
127.0.0.1 www.my-etrust.com
127.0.0.1 download.mcafee.com
127.0.0.1 dispatch.mcafee.com
127.0.0.1 secure.nai.com
127.0.0.1 nai.com
127.0.0.1 www.nai.com
127.0.0.1 update.symantec.com
127.0.0.1 updates.symantec.com
127.0.0.1 us.mcafee.com
127.0.0.1 liveupdate.symantec.com
127.0.0.1 customer.symantec.com
127.0.0.1 rads.mcafee.com
127.0.0.1 trendmicro.com
127.0.0.1 www.trendmicro.com
127.0.0.1 www.grisoft.com

…to prevent accessing these sites for updating antivirus software.

Then the trojan kills services with the following names:

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

After that, the trojan scans for "mysuperprog.exe" if this file is detected it will be deleted.
Note: The trojan creates its own thread for this purpose.

The trojan will rename antivirus and firewall releated files.
This DLL thread also renames files belonging to security and anti-virus software. The following files get renamed:

CCSETMGR.EXE
CCEVTMGR.EXE
NAVAPSVC.EXE
NPFMNTOR.EXE
symlcsvc.exe
SPBBCSvc.exe
SNDSrvc.exe
ccApp.exe
ccl30.dll
ccvrtrst.dll
LUALL.EXE
AUPDATE.EXE
Luupdate.exe
LUINSDLL.DLL
RuLaunch.exe
CMGrdian.exe
Mcshield.exe
outpost.exe
Avconsol.exe
Vshwin32.exe
VsStat.exe
Avsynmgr.exe
kavmm.exe
Up2Date.exe
KAV.exe
avgcc.exe
avgemc.exe
zonealarm.exe
zatutor.exe
zlavscan.dll
zlclient.exe
isafe.exe
cafix.exe
vsvault.dll
av.dll
vetredir.dll

…with these names:

C1CSETMGR.EXE
CC1EVTMGR.EXE
NAV1APSVC.EXE
NPFM1NTOR.EXE
s1ymlcsvc.exe
SP1BBCSvc.exe
SND1Srvc.exe
ccA1pp.exe
cc1l30.dll
ccv1rtrst.dll
LUAL1L.EXE
AUPD1ATE.EXE
Luup1date.exe
LUI1NSDLL.DLL
RuLa1unch.exe
CM1Grdian.exe
Mcsh1ield.exe
outp1ost.exe
Avc1onsol.exe
Vshw1in32.exe
Vs1Stat.exe
Av1synmgr.exe
kav12mm.exe
Up222Date.exe
K2A2V.exe
avgc3c.exe
avg23emc.exe
zonealarm.exe
zatutor.exe
zlavscan.dll
zo3nealarm.exe
zatu6tor.exe
zl5avscan.dll
zlcli6ent.exe
is5a6fe.exe
c6a5fix.exe
vs6va5ult.dll
a5v.dll
ve6tre5dir.dll

Note: All the affected software keeps working until next system restart. After restart all affected software will stop working because its files were renamed by the trojan.

After this the trojan terminates services with the following names:

SharedAccess
wscsvc

In the next step the trojan creates a thread that kills processes with the following names:

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

Finally the trojan tries to download a file from several webservers. The file is stored into the Windows directory as '_re_file.exe' and is executed via ShellExecute. The trojan tries to download from the following internet locations:

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

Note: Some of the URL's are included twice in the downloader.