W32.Tuoba.Trojan

W32.Tuoba.Trojan is installed by visiting a malicious Web page. The Web page uses an Internet Explorer exploit to execute the Content.php file, which is a malicious CHM file.

Content.php contains three files:

• Index.html, which uses an Internet Explorer exploit to download the file, Run.exe to C:\Program Files\En1857.exe, and then execute it. This file is detected as XMLid.Exploit.
• Htm2chm_explorer, which is not malicious.
• Htm2chm_about, which is not malicious.
  

When it is executed, Run.exe does the following:

1. Adds 213.159.118.226 to the local Intranet zone in Internet Explorer by modifying the values in the registry key:
   
   HKEY_USERS\.DEFAULT\Software\Microsoft\Windows\CurrentVersion\
   Internet Settings\ZoneMap\Ranges\Range1
   
   
2. Redirects requests to certain Web sites to the address 213.159.118.226. It does this by overwriting the Hosts file. These lines that are added to the file appear to mainly target Web sites, which adware automatically opens:
   

213.159.118.226 1-se.com
213.159.118.226 58q.com
213.159.118.226 aifind.cc
213.159.118.226 aifind.info
213.159.118.226 allneedsearch.com
213.159.118.226 approvedlinks.com
213.159.118.226 auto.ie.searchforge.com
213.159.118.226 awebfind.biz
213.159.118.226 best.royalsearch.net
213.159.118.226 cracks.am
213.159.118.226 default-homepage-network.com
213.159.118.226 find.microgirls.com
213.159.118.226 find4u.net
213.159.118.226 freshvideogals.com
213.159.118.226 i-lookup.com
213.159.118.226 ie-search.com
213.159.118.226 in.webcounter.cc
213.159.118.226 itseasy.us
213.159.118.226 just.find-itnow.com
213.159.118.226 link.startmake.com
213.159.118.226 mysearchnow.com
213.159.118.226 nativehardcore.com
213.159.118.226 qwertysearch123.biz
213.159.118.226 search.ieplugin.com
213.159.118.226 search.psn.cn
213.159.118.226 searchbar.findthewebsiteyouneed.com
213.159.118.226 searchcentrix.com
213.159.118.226 searchmyrequest.com
213.159.118.226 super-spider.com
213.159.118.226 t.rack.cc
213.159.118.226 teen-biz.com
213.159.118.226 teenhqpics.com
213.159.118.226 tits.hardcore4ever.net
213.159.118.226 webcoolsearch.com
213.159.118.226 wmmse.com
213.159.118.226 www.008i.com
213.159.118.226 www.2fastsearch.net
213.159.118.226 www.8095.com
213.159.118.226 www.alfa-search.com
213.159.118.226 www.boredlife.com
213.159.118.226 www.couldnotfind.com
213.159.118.226 www.cracks.am
213.159.118.226 www.daum.net
213.159.118.226 www.dreamwiz.com
213.159.118.226 www.find-itnow.com
213.159.118.226 www.find-itnow.com
213.159.118.226 www.find4u.net
213.159.118.226 www.firstbookmark.com
213.159.118.226 www.gajai.com
213.159.118.226 www.hand-book.com
213.159.118.226 www.hao123.com
213.159.118.226 www.hotsearchbox.com
213.159.118.226 www.hotwebsearch.com
213.159.118.226 www.hugesearch.net
213.159.118.226 www.iquicksearch.com
213.159.118.226 www.lookfor.cc
213.159.118.226 www.maxxxhosters.com
213.159.118.226 www.naver.com
213.159.118.226 www.nkvd.us
213.159.118.226 www.novafuck.com
213.159.118.226 www.ohcorea.com
213.159.118.226 www.omega-search.com
213.159.118.226 www.onet.pl
213.159.118.226 www.power-search.info
213.159.118.226 www.rightfinder.net
213.159.118.226 www.search-1.net
213.159.118.226 www.search-and-go.com
213.159.118.226 www.search-dot.com
213.159.118.226 www.search-space.com
213.159.118.226 www.searchforge.com
213.159.118.226 www.searching-the-net.com
213.159.118.226 www.searchv.com
213.159.118.226 www.searchxl.com
213.159.118.226 www.seznam.cz
213.159.118.226 www.slotch.com
213.159.118.226 www.spidersearch.com
213.159.118.226 www.startium.com
213.159.118.226 www.therealsearch.com
213.159.118.226 www.ttjj.com
213.159.118.226 www.viewpornkey.com
213.159.118.226 www.wazzupnet.com
213.159.118.226 www.websearch.com
213.159.118.226 www.windowws.cc
213.159.118.226 www.xgmm.com
213.159.118.226 xwebsearch.biz
213.159.118.226 yourbookmarks.ws

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.

Summary