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Win32/Conficker
(?)
Encyclopedia entry
Updated:
Apr 17, 2011
| Published:
Jan 08, 2009
Aliases
TA08-297A
(other)
-
CVE-2008-4250
(other)
-
VU827267
(other)
-
Win32/Conficker.A
(CA)
-
Mal/Conficker-A
(Sophos)
-
Trojan.Win32.Agent.bccs
(Kaspersky)
-
W32.Downadup.B
(Symantec)
-
Trojan-Downloader.Win32.Agent.aqfw
(Kaspersky)
-
W32/Conficker.worm
(McAfee)
-
Trojan:Win32/Conficker!corrupt
(Microsoft)
-
W32.Downadup
(Symantec)
-
WORM_DOWNAD
(Trend Micro)
-
Confickr
(other)
Alert Level
(?)
Severe
Antimalware protection details
Microsoft recommends that you download the
latest definitions
to get protected.
Summary
Win32/Conficker is a worm that infects other computers across a network by exploiting a vulnerability in the Windows Server service (SVCHOST.EXE). If the vulnerability is successfully exploited, it could allow remote code execution when file sharing is enabled. Depending on the specific variant, it may also spread via removable drives and by exploiting weak passwords. It disables several important system services and security products and downloads arbitrary files.
Microsoft also recommends that users ensure that their network passwords are strong to prevent this worm from spreading via weak administrator passwords. More information is available here.
Microsoft also recommends that users apply an update that changes the AutoPlay functionality in Windows to prevent this worm from spreading via USB drives. More information is available in the
Microsoft Knowledgebase Article KB971029
.
Variant Comparison
There have been several variants of Conficker reported from the wild. The following table summarizes and distinguishes the critical features of each variant:
|
Variant
|
Spreads Via…
|
Payload
|
Additional Information
|
|
21st Nov 2008
Payload Trigger Date:
25 Nov 2008 and later
|
-Exploiting the vulnerability outlined in Security Bulletin MS08-067.
|
-Generates 250 URLs daily that it checks for updates
-Resets System Restore Point
|
The name of this family was derived by selecting fragments from
'trafficconverter.biz',
a string found in this variant.
|
|
Discovered Date:
29th Dec 2008
Payload Trigger Date:
1 January 2009 and later
|
In addition to the method used by the .A variant (above):
-Network shares with weak passwords
-Mapped and Removable drives
-Uses a scheduled task to execute copies of the worm on targeted machines
|
In addition to the .A variant's Payload (above - although .B uses a different method to generate URLs):
- Blocks access to many security-related websites
-Modifies system settings
-Terminates system and security services
|
This variant built on the functionality of the .A variant by adding new spreading mechanisms and by making itself more difficult to remove.
|
|
Discovered Date:
20th Feb 2009
Payload Trigger Date:
1 January 2009 and later
|
Uses the same methods listed above for the .B variant.
|
In addition to the Payloads listed above for .A and .B:
- Uses additional method for downloading files that utilizes Peer-to-Peer communications
- Adds checks to verify the authenticity/validity of content targeted for download
|
Very similar to the .B variant in function (this variant has even been referred to as variant .B++).
|
|
Discovered Date:
4th Mar 2009
Payload Trigger Date:
1st April 2009 and later
|
No spreading functionality per se. Distributed as an update to machines previously infected with the .B and .C variants.
|
In addition to the Payloads listed above for .A and .B, with some variations:
- Generates 50,000 URLs to download files from. This variant only visits 500 of the generated URLs within a 24-hour period.
- Expands on efforts to hinder its removal from an affected machine.
|
Spreading functionality was removed from this variant. It continues to expand on its file downloading payload and targets a broader range of processes to terminate (appears to be targeting cleaning utilities designed specifically to remove Conficker). It also blocks access to additional security-related websites.
|
|
Discovered Date:
8th Apr 2009
Payload Trigger Date:
1st April 2009 and later
|
No spreading functionality per se. Utilized to update machines previously infected with the .B and .C and .D variants.
|
- Blocks access to many security-related websites
-Modifies system settings
-Terminates system and security services
-Terminates itself on May 3
|
May have been distributed via the Conficker peer-to-peer network.
|
Please see the individual descriptions of each variant, elsewhere in our encyclopedia for further, detailed variant-specific analysis.
Symptoms
System Changes
The following system changes may indicate the presence of this malware:
- The following services are disabled or fail to run:
Windows Security Center Service
Windows Update Auto Update Service
Background Intelligence Transfer Service
Windows Defender
Error Reporting Service
Windows Error Reporting Service
- Users may not be able to connect to websites or online services that contain the following strings:
virus
spyware
malware
rootkit
defender
microsoft
symantec
norton
mcafee
trendmicro
sophos
panda
etrust
networkassociates
computerassociates
f-secure
kaspersky
jotti
f-prot
nod32
eset
grisoft
drweb
centralcommand
ahnlab
esafe
avast
avira
quickheal
comodo
clamav
ewido
fortinet
gdata
hacksoft
hauri
ikarus
k7computing
norman
pctools
prevx
rising
securecomputing
sunbelt
emsisoft
arcabit
cpsecure
spamhaus
castlecops
threatexpert
wilderssecurity
windowsupdate
Technical Information (Analysis)
Win32/Conficker is a worm that infects other computers across a network by exploiting a vulnerability in the Windows Server service (SVCHOST.EXE). If the vulnerability is successfully exploited, it could allow remote code execution when file sharing is enabled. Depending on the specific variant, it may also spread via removable drives and by exploiting weak passwords. It disables several important system services and security products and downloads arbitrary files.
Microsoft also recommends that users ensure that their network passwords are strong to prevent this worm from spreading via weak administrator passwords. More information is available here.
Variant Comparison
There have been several variants of Conficker reported from the wild. The following table summarizes and distinguishes the critical features of each variant:
|
Variant
|
Spreads Via…
|
Payload
|
Additional Information
|
|
21st Nov 2008
Payload Trigger Date:
25 Nov 2008 and later
|
-Exploiting the vulnerability outlined in Security Bulletin MS08-067.
|
-Generates 250 URLs daily that it checks for updates
-Resets System Restore Point
|
The name of this family was derived by selecting fragments from
'trafficconverter.biz',
a string found in this variant.
|
|
Discovered Date:
29th Dec 2008
Payload Trigger Date:
1 January 2009 and later
|
In addition to the method used by the .A variant (above):
-Network shares with weak passwords
-Mapped and Removable drives
-Uses a scheduled task to execute copies of the worm on targeted machines
|
In addition to the .A variant's Payload (above - although .B uses a different method to generate URLs):
- Blocks access to many security-related websites
-Modifies system settings
-Terminates system and security services
|
This variant built on the functionality of the .A variant by adding new spreading mechanisms and by making itself more difficult to remove.
|
|
Discovered Date:
20th Feb 2009
Payload Trigger Date:
1 January 2009 and later
|
Uses the same methods listed above for the .B variant.
|
In addition to the Payloads listed above for .A and .B:
- Uses additional method for downloading files that utilizes Peer-to-Peer communications
- Adds checks to verify the authenticity/validity of content targeted for download
|
Very similar to the .B variant in function (this variant has even been referred to as variant .B++).
|
|
Discovered Date:
4th Mar 2009
Payload Trigger Date:
1st April 2009 and later
|
No spreading functionality per se. Distributed as an update to machines previously infected with the .B and .C variants.
|
In addition to the Payloads listed above for .A and .B, with some variations:
- Generates 50,000 URLs to download files from. This variant only visits 500 of the generated URLs within a 24-hour period.
- Expands on efforts to hinder its removal from an affected machine.
|
Spreading functionality was removed from this variant. It continues to expand on its file downloading payload and targets a broader range of processes to terminate (appears to be targeting cleaning utilities designed specifically to remove Conficker). It also blocks access to additional security-related websites.
|
|
Discovered Date:
8th Apr 2009
Payload Trigger Date:
No Payload trigger date
|
In addition to the method used by the .A variant (above):
-Network shares with weak passwords
|
- Blocks access to many security-related websites
-Modifies system settings
-Terminates system and security services
-Terminates itself on May 3
|
This variant built on the functionality of the .A variant by adding new spreading mechanisms and by making itself more difficult to remove.
|
Please see the individual descriptions of each variant, elsewhere in our encyclopedia for further, detailed variant-specific analysis.
Prevention
Take the following steps to help prevent infection on your computer:
-
Enable a firewall on your computer.
-
Get the latest computer updates for all your installed software.
-
Use up-to-date antivirus software.
-
Limit user privileges on the computer.
-
Use caution when opening attachments and accepting file transfers.
-
Use caution when clicking on links to Web pages.
-
Avoid downloading pirated software.
-
Protect yourself against social engineering attacks.
-
Use strong passwords.
Enable a firewall on your computer
Use a third-party firewall product or turn on the Microsoft Windows Internet Connection Firewall.
Get the latest computer updates
Updates help protect your computer from viruses, worms, and other threats as they are discovered. It is important to install updates for all the software that is installed in your computer. These are usually available from vendor Web sites.
You can use the Automatic Updates feature in Windows to automatically download future Microsoft security updates while your computer is on and connected to the Internet.
Use up-to-date antivirus software
Limit user privileges on the computer
Starting with Windows Vista and Windows 7, Microsoft introduced User Account Control (UAC), which, when enabled, allowed users to run with least user privileges. This scenario limits the possibility of attacks by malware and other threats that require administrative privileges to run.
You can configure UAC in your computer to meet your preferences:
Use caution when opening attachments and accepting file transfers
Exercise caution with e-mail and attachments received from unknown sources, or received unexpectedly from known sources. Use extreme caution when accepting file transfers from known or unknown sources.
Use caution when clicking on links to Web pages
Exercise caution with links to Web pages that you receive from unknown sources, especially if the links are to a Web page that you are not familiar with, unsure of the destination of, or suspicious of. Malicious software may be installed in your computer simply by visiting a Web page with harmful content.
Avoid downloading pirated software
Threats may also be bundled with software and files that are available for download on various torrent sites. Downloading "cracked" or "pirated" software from these sites carries not only the risk of being infected with malware, but is also illegal. For more information, see ' The risks of obtaining and using pirated software'.
Protect yourself from social engineering attacks
While attackers may attempt to exploit vulnerabilities in hardware or software to compromise a computer, they also attempt to exploit vulnerabilities in human behavior to do the same. When an attacker attempts to take advantage of human behavior to persuade the affected user to perform an action of the attacker's choice, it is known as 'social engineering'. Essentially, social engineering is an attack against the human interface of the targeted computer. For more information, see ' What is social engineering?'.
Use strong passwords
Attackers may try to gain access to your Windows account by guessing your password. It is therefore important that you use a strong password – one that cannot be easily guessed by an attacker. A strong password is one that has at least 8 characters, and combines letters, numbers, and symbols. For more information, see http://www.microsoft.com/protect/yourself/password/create.mspx.
Recovery
Microsoft also recommends that users ensure that their network passwords are strong to prevent this worm from spreading via weak administrator passwords. More information is available
here
.
Microsoft also recommends that users apply an update that changes the AutoPlay functionality in Windows to prevent this worm from spreading via USB drives. More information is available in the
Microsoft Knowledgebase Article KB971029
.
To detect and remove this threat and other malicious software that may be installed in your computer, run a full-system scan with an up-to-date antivirus product such as the following:
Note: Computers infected by Conficker may be unable to connect to web sites related to security applications and services that may otherwise assist in the removal of this worm (for example, downloading antivirus updates may fail). In this case users will need to use an uninfected computer in order to download any appropriate updates or tools and then transfer these to the infected computer.
Microsoft Help and Support have provided a detailed guide to removing a Conficker.B infection from an affected computer, either manually or by using the MSRT (Malicious Software Removal Tool).
For detailed instructions on how to manually remove Conficker.B, view the following article using an uninfected computer:
Additional information on deploying MSRT in an enterprise environment can be found here:
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