W32.Chod@mm
Discovered on: March 13, 2005
Last Updated on: November 04, 2005 11:22:06 AM







W32.Chod@mm is a mass-mailing worm that also propagates using MSN Messenger. The worm has back door capabilities and can be controlled through IRC channels. It also overwrites the Hosts file and lowers security settings.

Also Known As: Win32.Nochod.{A, S} [Computer Associates], Tobecho.A [Panda Software], W32/NoChod@MM [McAfee], WORM_CHOD.{A, B} [Trend Micro]

Type: Worm
Infection Length: 152,292 bytes



Systems Affected: Windows 2000, Windows 95, Windows 98, Windows Me, Windows NT, Windows Server 2003, Windows XP







Virus Definitions (LiveUpdate™ Weekly)
March 16, 2005


Virus Definitions (Intelligent Updater)
March 14, 2005







Wild

Number of infections: 0 - 49
Number of sites: 0 - 2
Geographical distribution: Low
Threat containment: Easy
Removal: Moderate
Threat Metrics


Wild:
Low
Damage:
Medium
Distribution:
High



Damage

Payload Trigger: n/a
Payload: Opens and back door.
Large scale e-mailing: Sends an email to addresses gathered from the compromised computer.
Deletes files: n/a
Modifies files: Modifies the Hosts file.
Degrades performance: Performance may be degraded when a denial of service attack is being launched.
Causes system instability: n/a
Releases confidential info: Steals passwords for various applications.
Compromises security settings: Ends security-related processes and blocks access to various security-related Web sites.
Distribution

Subject of email: Varies
Name of attachment: Varies with .exe, .pif, or .scr file extension
Size of attachment: 152,292 bytes
Time stamp of attachment: n/a
Ports: n/a
Shared drives: n/a
Target of infection: Attempts to spread via MSN Messenger.


When W32.Chod@mm is executed, it performs the following actions:


Drops the following files:


%System%\cpu.dll
%System%\<random folder name>\csrss.dat
%System%\<random folder name>\csrss.exe
%System%\<random folder name>\csrss.ini

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).


Drops the shortcut C:\Documents and Settings\All Users\Start Menu\Programs\Startup\csrss.lnk.


Adds the value:

“Csrss” = "%System%\[random folder name]\csrss.exe“

to the registry keys:

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

so that W32.Chod@mm runs every time Windows starts.


Adds the value:

”Installed“ = ”1“

to the registry subkeys:

HKEY_CLASSES_ROOT\Chode
HKEY_LOCAL_MACHINE\Software\Classes\Chode
HKEY_CURRENT_USER\Software\Chode

as an infection marker.


Adds the values:

”DisableRegistryTools“ = ”1“
”NoAdminPage“ = ”1“

to the registry subkey:

HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\
Policies\System

to disable registry tools.


Adds the value:

”DisableSR“ = ”1“

to the registry subkey:

HKEY_LOCAL_MACHINE\Software\Microsoft\Windows NT\CurrentVersion\SystemRestore

to disable system restore.

Adds the values:

”Hidden“ = ”2“
”SuperHidden“ = ”0“
”ShowSuperHidden“ = ”0“

to the registry subkey:

HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced

to hide the dropped file.


Adds the following lines to the win.ini file so that the worm is executed every time Windows starts:

”Load“ = ”%System%\csrss.exe“
”Run“ = ”%System%\csrss.exe“


Adds the values:

”Run“ = ”%System%\[random folder name]\csrss.exe“
”Load“ = ”%System%\[random folder name]\csrss.exe“

to the registry subkey:

HKEY_CURRENT_USER\Software\Microsoft\Windows NT\CurrentVersion\Windows

so that the worm is executed every time Windows starts.


Deletes the values:

”MCAgentExe“
”ISSVC“
”navapsvc“
”Symantec“
”Run\LC“
”ccEvtMgr“
”SNDSrvc“
”ccProxy“
”ccPwdSvc“
”ccSetMgr“
”SPBBCSvc“
”SAVScan“
”SBService“
”SmcService“
”OutpostFirewal“
”l“
”vsmon“
”CAISafe“
”net stop“
”scconfig“
”CleanUp“
”MCUpdateExe“
”VirusScan“
”Online“
”VSOCheckTask“
”ccApp“
”mcvsrte.exe“
”Symantec NetDriver Monitor“
”Outpost“
”Firewall“
”gcasServ“
”KAVPerson“
”al50“
”Zone Labs Client“
”services“
”microsoftantispyware“
”hijackthis“

from the registry subkey:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run

to prevent several applications that are associated with the above registry keys from running at system startup.


Modifies the Hosts file to block access to the following Web sites:


avp.com
ca.com
customer.symantec.com
dispatch.mcafee.com
download.mcafee.com
f-secure.com
fastclick.net
ftp.f-secure.com
ftp.sophos.com
grisoft.com
housecall.trendmicro.com
kaspersky.com
liveupdate.symantec.com
mast.mcafee.com
mcafee.com
merijn.org
my-etrust.com
nai.com
networkassociates.com
pandasoftware.com
phpbb.com
rads.mcafee.com
secure.nai.com
securityresponse.symantec.com
service1.symantec.com
sophos.com
spywareinfo.com
support.microsoft.com
symantec.com
trendmicro.com
update.symantec.com
updates.symantec.com
us.mcafee.com
vil.nai.com
viruslist.com
www.avp.com
www.awaps.net
www.ca.com
www.f-secure.com
www.fastclick.net
www.grisoft.com
www.kaspersky.com
www.mcafee.com
www.merijn.org
www.microsoft.com
www.my-etrust.com
www.nai.com
www.networkassociates.com
www.pandasoftware.com
www.phpbb.com
www.sophos.com
www.spywareinfo.com
www.symantec.com
www.trendmicro.com
www.viruslist.com
www.zonelabs.com
www3.ca.com
zonelabs.com


Ends the following processes, some of which may be security-related:


bbeagle.exe
ccapp.exe
ccevtmgr.exe
ccproxy.exe
ccsetmgr.exe
d3dupdate.exe
enterprise.exe
gcasdtserv.exe
gcasserv.exe
hijackthis.exe
i11r54n4.exe
irun4.exe
isafe.exe
issvc.exe
kav.exe
kavsvc.exe
mcagent.exe
mcdash.exe
mcinfo.exe
mcmnhdlr.exe
mcshield.exe
mcvsescn.exe
mcvsftsn.exe
mcvsshld.exe
mpfagent.exe
mpfservice.exe
mpftray.exe
msblast.exe
msconfig.exe
mscvb32.exe
mskagent.exe
mwincfg32.exe
navapsvc.exe
navapw32.exe
navw32.exe
npfmntor.exe
outpost.exe
pandaavengine.exe
penis32.exe
regedit.exe
smc.exe
sndsrvc.exe
spbbcsvc.exe
symlcsvc.exe
sysinfo.exe
sysmonxp.exe
teekids.exe
usrprmpt.exe
vsmon.exe
wincfg32.exe
winsys.exe


May attempt to disable the following services:


gcasServ
hijackthis*
KAVPersonal50
microsoft antispyware*
Outpost Firewall
services
Symantec NetDriver Monitor
Zone Labs Client


Opens a back door to a remote IRC server and allows a remote attacker to have unauthorized access to the compromised computer.


Listens for commands from the attacker to perform some of the following actions:


Shut down and reboot the computer
Download and execute files
Perform ping, TCP, or UDP denial of service attacks
Get local host information
Spread through MSN messenger
Spread via email


Attempts to steal passwords for any of the following applications:


AOL Instant Messenger (in old versions)
AOL Instant Messenger/Netscape 7
GAIM
ICQ Lite 4.x/2003
Miranda
MSN Messenger
Trillian
Windows Messenger (on Windows XP)
Yahoo Messenger (Versions 5.x and 6.x)


Uses one of the following tools to steal passwords from the above application:


Intelligent TCPIP.SYS patcher
MessenPass
Protected Storage PassView


The worm then collects email addresses from files with the following extensions:


.adb
.asp
.cg
.ctt
.dbx
.dhtm
.doc
.eml
.htm
.html
.msg
.oft
.php
.pl
.rtf
.sht
.shtm
.sql
.tbb
.txt
.uin
.vbs
.wab
.xml

Avoids sending itself to addresses with domain names containing the following strings:


antivirus
avp
bitdefender
f-pro
f-secure
mcafee
messagelabs
Microsoft
spam
symantec


Uses its own SMTP engine to send a copy of itself to the email addresses gathered.

The email has the following characteristics:

From:
One of the following:


security@microsoft.com
security@trendmicro.com
securityresponse@symantec.com

Subject:
One of the following:


Warning - you have been infected!
Your computer may have been infected

Message:

Your message was undeliverable due to the following reason(s):
Your message could not be delivered because the destination server was unreachable within the allowed queue period. The amount of time a message is
queued before it is returned depends on local configuration parameters. Most likely there is a network problem that prevented delivery, but it is also possible
that the computer is turned off, or does not have a mail system running right now. Your original message has been attached.

Attachment:
One of the following:


message.pif
message.scr
netsky_removal.exe
removal_tool.exe


Sends a copy of itself through MSN Messenger. The message has the following characteristics:

Message:
One of the following:


lol check this out, it freaked me out :S
LOL! look at this, I can't explain it in words…
omg check this out, it's just wrong :O
ROFL!! you have to see this… wtf…
you have to see this, it's amazing!

Attachment:
One of the following:


awesome
gross
mypic
naked lesbian twister
paris hilton
picture
us together


with one of the following extensions:


.exe
.scr






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

Turn off and remove unneeded services. By default, many operating systems install auxiliary services that are not critical, such as an FTP server, telnet, and a Web server. These services are avenues of attack. If they are removed, blended threats have less avenues of attack and you have fewer services to maintain through patch updates.
If a blended 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 (for example, all Windows-based computers should have the current Service Pack installed.). Additionally, please apply any security updates that are mentioned in this writeup, in trusted Security Bulletins, or on vendor Web sites.
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.
Configure your email server to block or remove email that contains file attachments that are commonly used to spread viruses, such as .vbs, .bat, .exe, .pif and .scr files.
Isolate infected computers quickly to prevent further compromising your organization. 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.


The following instructions pertain to all current and recent Symantec antivirus products, including the Symantec AntiVirus and Norton AntiVirus product lines.


Disable System Restore (Windows Me/XP).
Restart the computer in Safe Mode.
Delete the values that were added to the registry.
Reinstall your Symantec AntiVirus Product.
Update the virus definitions.
Run a full system scan and delete all the files detected as W32.Chod@mm.
Edit the win.ini file.

For specific details on each of these steps, read the following instructions.

1. To disable System Restore (Windows Me/XP)
If you are running Windows Me or Windows XP, we recommend that you temporarily turn off System Restore. Windows Me/XP uses this feature, which is enabled by default, to restore the files on your computer in case they become damaged. If a virus, worm, or Trojan infects a computer, System Restore may back up the virus, worm, or Trojan on the computer.

Windows prevents outside programs, including antivirus programs, from modifying System Restore. Therefore, antivirus programs or tools cannot remove threats in the System Restore folder. As a result, System Restore has the potential of restoring an infected file on your computer, even after you have cleaned the infected files from all the other locations.

Also, a virus scan may detect a threat in the System Restore folder even though you have removed the threat.

For instructions on how to turn off System Restore, read your Windows documentation, or one of the following articles:
”How to disable or enable Windows Me System Restore“
”How to turn off or turn on Windows XP System Restore“

Note: When you are completely finished with the removal procedure and are satisfied that the threat has been removed, re-enable System Restore by following the instructions in the aforementioned documents.

For additional information, and an alternative to disabling Windows Me System Restore, see the Microsoft Knowledge Base article, ”Antivirus Tools Cannot Clean Infected Files in the _Restore Folder,“ Article ID: Q263455.


2. To restart the computer in Safe mode or VGA mode
Shut down the computer and turn off the power. Wait for at least 30 seconds, and then restart the computer in Safe mode or VGA mode.
For Windows 95, 98, Me, 2000, or XP users, restart the computer in Safe mode. For instructions, read the document, ”How to start the computer in Safe Mode.“
For Windows NT 4 users, restart the computer in VGA mode.

Note: Step 4 should be completed while in Safe mode.


3. To delete the value from the registry
Important: Symantec strongly recommends that you back up the registry before making any changes to it. Incorrect changes to the registry can result in permanent data loss or corrupted files. Modify the specified subkeys only. Read the document, ”How to make a backup of the Windows registry,“ for instructions.

Click Start > Run.
Type regedit

Then click OK.


Navigate to the subkeys:

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


In the right pane, delete the value:

”Csrss“ = ”%System%\[random folder name]\csrss.exe“


Navigate to the subkey:

HKEY_CURRENT_USER\Software\Microsoft\Windows NT\CurrentVersion\Windows


In the righ pane, delete the values:

”Load“ = ”%System%\[random folder name]\csrss.exe“
”Run“ = ”%System%\[random folder name]\csrss.exe“


Navigate to the registry subkeys:

HKEY_CLASSES_ROOT\Chode
HKEY_LOCAL_MACHINE\Software\Classes\Chode
HKEY_CURRENT_USER\Software\Chode


In the right pane, delete the value:

”Installed“ = ”1“


Navigate to the registry subkey:

HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\
Policies\System


In the right pane, delete the values:

”DisableRegistryTools“ = ”1“
”NoAdminPage“ = ”1“


Navigate to the registry subkey:

HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\
Explorer\Advanced


In the right pane, delete the values:

”Hidden“ = ”2“
”SuperHidden“ = ”0“
”ShowSuperHidden“ = ”0“


Exit the Registry Editor.


4. To reinstall your Symantec antivirus program
As this virus attempts to remove the files and registry subkeys that your Symantec antivirus program uses, you may need to reinstall the program. If your Symantec antivirus program is not working properly, uninstall, and then reinstall it. For instructions on how to do this, please consult the documentation that came with your Symantec product.

Restart the computer in Normal mode and proceed with section 5.


5. To update the virus definitions
Symantec Security Response fully tests all the virus definitions for quality assurance before they are posted to our servers. There are two ways to obtain the most recent virus definitions:
Running LiveUpdate, which is the easiest way to obtain virus definitions: These virus definitions are posted to the LiveUpdate servers once each week (usually on Wednesdays), unless there is a major virus outbreak. To determine whether definitions for this threat are available by LiveUpdate, refer to the Virus Definitions (LiveUpdate).
Downloading the definitions using the Intelligent Updater: The Intelligent Updater virus definitions are posted daily. You should download the definitions from the Symantec Security Response Web site and manually install them. To determine whether definitions for this threat are available by the Intelligent Updater, refer to the Virus Definitions (Intelligent Updater).

The Intelligent Updater virus definitions are available: Read ”How to update virus definition files using the Intelligent Updater“ for detailed instructions.

Note: If you see an error, such as LU1418, when you try to run LiveUpdate and you cannot get the Web site hosting the Intelligent Updater, it is likely that the worm has modified the Hosts file. You can either download and install LiveUpdate 2.5, which can remove Symantec entries from that file, or you can edit it yourself. See the instructions for both in the ”Additional Information“ section below.

6. To scan for and delete the infected files
Start your Symantec antivirus program and make sure that it is configured to scan all the files.
For Norton AntiVirus consumer products: Read the document, ”How to configure Norton AntiVirus to scan all files.“
For Symantec AntiVirus Enterprise products: Read the document, ”How to verify that a Symantec Corporate antivirus product is set to scan all files.“
Run a full system scan.
If any files are detected as infected with W32.Chod@mm, click Delete.

Note: If your Symantec antivirus product reports that it cannot delete an infected file, Windows may be using the file. To fix this, run the scan in Safe mode. For instructions, read the document, ”How to start the computer in Safe Mode." Once you have restarted in Safe mode, run the scan again.

After the files are deleted, restart the computer in Normal mode and proceed with section 4.


7. Edit the Win.ini file
If you are running Windows 95/98/Me, follow these steps:

Click Start > Run.
Type the following:

edit c:\windows\win.ini

and then click OK.

(The MS-DOS Editor opens.)

NOTE: If Windows is installed in a different location, make the appropriate path substitution.


In the [windows] section of the file, look for a line similar to:

“Run” = “%System%\csrss.exe”


If this line exists, delete everything to the right of run=


In the [windows] section of the file, look for a line similar to:

“Load” = “%System%\csrss.exe”


If the line exists, delete everything to the right of load=


Click File > Save.


Click File > Exit.





Additional information:

Removing entries from the Hosts file
If this threat has modified the Windows Hosts file, there are two ways to remove these entries:

Install and run the current version of LiveUpdate. This will remove only the entries that refer to Symantec domains.
Manually edit the Hosts file and remove all the entries that the worm added.

To run the current version of LiveUpdate
Click download LiveUpdate.

Note: If you are not reading this Web page on the computer that is getting the error notice, the address for downloading the file is:

ftp://ftp.symantec.com/public/english_us_canada/liveupdate/lusetup.exe

If necessary, you can type this address into the address bar of the problem computer. Changes to the Hosts file will not stop you from getting to this site.


Save the file to the Windows desktop.
Double-click the lusetup.exe icon on the desktop to install LiveUpdate.
Run LiveUpdate.
Did you see the message “LU1860: LiveUpdate has detected a potential security compromise on your computer”?
If you did, let LiveUpdate “Remove these entries from the hosts files” (Recommended).
This should allow LiveUpdate to run.
If you did not, that was not the cause of the problem. Return to the Removal section.


To manually edit the Hosts file and remove all the entries that the worm added

Note: The location of the Hosts file may vary and some computers may not have this file. For example, if the file exists in Windows 98, it will usually be in C:\Windows; and it is located in the C:\WINNT\system32\drivers\etc folder in Windows 2000. There may also be multiple copies of this file in different locations.


Follow the instructions for your operating system:
Windows 95/98/Me/NT/2000
Click Start, point to Find or Search, and then click Files or Folders.
Make sure that “Look in” is set to (C:) and that “Include subfolders” is checked.
In the “Named” or “Search for…” box, type:

hosts


Click Find Now or Search Now.
For each Hosts file that you find, right-click the file, and then click Open With.
Deselect the “Always use this program to open this program” check box.
Scroll through the list of programs and double-click Notepad.
When the file opens, delete all the entries the reference the Web sites listed in Step 10 of the “Technical Details” section.
Close Notepad and save your changes when prompted.


Windows XP
Click Start > Search.
Click All files and folders.
In the “All or part of the file name” box, type:

hosts


Verify that “Look in” is set to “Local Hard Drives” or to (C:).
Click More advanced options.
Check Search system folders.
Check Search subfolders.
Click Search.
Click Find Now or Search Now.
For each Hosts file that you find, right-click the file, and then click Open With.
Deselect the Always use this program to open this program check box.
Scroll through the list of programs and double-click Notepad.
When the file opens, delete all the entries the reference the Web sites listed in Step 10 of the “Technical Details” section.
Close Notepad and save your changes when prompted.