1. Symantec/
  2. Security Response/
  3. Trojan.Zefarch


Risk Level 1: Very Low

January 27, 2009
July 8, 2013 8:36:55 AM
Also Known As:
Hiloti [Panda Software]
Infection Length:
134,656 bytes
Systems Affected:
When executed, the Trojan copies itself as the following file:

It may also create the following files:
  • %UserProfile%\Application Data\Mozilla\Firefox\Extensions\chrome.manifest
  • %UserProfile%\Application Data\Mozilla\Firefox\Extensions\install.rdf
  • %UserProfile%\Application Data\Mozilla\Firefox\Extensions\chrome\content\_cfg.js
  • %UserProfile%\Application Data\Mozilla\Firefox\Extensions\chrome\content\c.js
  • %UserProfile%\Application Data\Mozilla\Firefox\Extensions\chrome\content\overlay.xul

It then creates the following registry entry so that it runs every time Windows starts:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run\"[RANDOM CHARACTERS]" = "rundll32.exe "%Windir%\[RANDOM CHARACTERS].dll",e"

Note: The threat monitors the above registry entry and will recreate it if it is modified or deleted.

It then creates the following registry entries to register itself as a Browser Helper Object (BHO) for Internet Explorer:
  • HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\Browser Helper Objects\[RANDOM CLSID]\"(Default)" = "%Windir%\[RANDOM CHARACTERS].dll"
  • HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Browser Helper Objects\[RANDOM CLSID]\"(Default)" = "%Windir%\[RANDOM CHARACTERS].dll"

It then creates the following registry subkey to register itself as an extension for Mozilla Firefox:

The Firefox extension monitors URLs accessed on the compromised computer for the following strings:
  • google
  • yahoo
  • aol.com
  • live
  • msn
  • ask.com

If found, the Firefox extension inserts JavaScript from the following network address into the search results:

It may also connect to the following IP addresses:

The Internet Explorer Browser Helper Object (BHO) monitors URLs accessed on the compromised computer for the following strings:
  • %2Faclk
  • .ah-ha.
  • .aol.com
  • .epilot.com
  • .gohip.
  • .google.
  • .live.
  • .msn.
  • .oingo.
  • .search123.
  • .teoma.
  • .wanadoo.
  • /search
  • /web?
  • ?aclk
  • 250000.co.uk
  • 7search.
  • about.
  • ads.ask.com
  • alexa.
  • alltheweb.com
  • allyoursearch.
  • altavista.
  • altavista.com
  • aol
  • aol.
  • asiaco.
  • ask.
  • askredir.com
  • bbc.
  • clearsearch.
  • comcast.
  • coolwebsearch.
  • crawlbar.
  • daum.net
  • destinationadult.
  • ditto.com
  • dmoz.
  • dogpile.
  • earthlink.
  • emetasearch.
  • exactsearch.
  • excite.
  • find=
  • findsearch.
  • findwhat.
  • galaxysearch.
  • gateway.com
  • genieknows.
  • gigablast.com
  • goclick.
  • goguides.
  • google
  • grip.com
  • hotbot.com
  • infoseek.
  • inquire.
  • instafinder.
  • jayde.
  • kanoodle.
  • keywords=
  • kw=
  • london-pages.co.uk
  • looksmart.
  • lycos.
  • mamma.
  • mirago.
  • mt=
  • mygeek.
  • myway.
  • mywebsearch.
  • navisearch.
  • neon.org
  • netscape.
  • netster.
  • netzero.
  • nytimes.
  • overture.
  • perfectnav.
  • phrase=
  • qkw=
  • qq=
  • qry=
  • qt=
  • qu=
  • query=
  • r.looksmart.com
  • reference.
  • revquest.
  • satitle=
  • sc=
  • scoutcrawl.
  • search
  • search.aol
  • search.lycos
  • search.yahoo.
  • search_str=
  • search=
  • searchengine.
  • searchfeed.
  • searchfor=
  • searchmiracle.
  • searchscout.
  • searchstri=
  • searchterm=
  • searchtext=
  • seeq.
  • sensis.com
  • sex.com
  • shoprogers.
  • sirsearch.
  • slirsredirect
  • slotch.
  • sqwire.
  • ss=
  • string=
  • term=
  • terms=
  • thefreedictionary.
  • ukindex.co.uk
  • url.searchuk.com
  • usseek.
  • vachercher.lycos.fr
  • vivisimo.
  • web.ask.co.uk
  • webmail.aol.com
  • websearch.
  • wesearchall.
  • what2find.
  • wikipedia.
  • wisenut.
  • word=
  • zeal.

It may redirect users to potentially malicious Web sites or insert code into Web pages whose URLs contain the above strings.


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: Gilou Tenebro
Summary| Technical Details| Removal

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