File names: Linmeimei.exe; Wupdate.exe
When Adware.CNS3721 is executed, it performs the following actions:
- Copies itself to %System%\Wupdate.exe.
Note: %System% is a variable. The worm locates the folder (by default, this is C:\Windows\System or C:\Winnt\System32) and copies itself to that location.
- Adds the value:
"Windows Update" = %System%\Wupdate.exe
to the registry key:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
so that the adware runs when you start Windows.
- Changes the Internet Explorer home page to we.cn.gs.
- Opens a browser window and displays a flash animation downloaded from the Internet.
- May contact the Web site, cns.3721.com, for advertising purposes.
- May download itself, or its updated version, from we.cn.gs.
Note: Removing this adware component from the system will likely cause the program that installed it to not function as intended. The uninstaller generally identifies the programs that will not work after uninstallation.
- Update the virus definitions.
- Run a full system scan and delete all the files detected as Adware.CNS3721.
- Delete the value from the Registry.
- Restore the Internet Explorer settings
For specific details on each of these steps, read the following instructions.
1. Updating 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 on U.S. business days (Monday through Friday). 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.
2. Scanning for and deleting the infected files
- Start Norton AntiVirus and make sure that it is configured to scan all the files. For more information, read the document, "How to configure Norton AntiVirus to scan all files."
- Run a full system scan.
- If any files are detected as infected with Adware.CNS3721, click Delete.
3. Deleting the value from the registry
CAUTION: 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 keys only. Read the document, "How to make a backup of the Windows registry," for instructions.
- Click Start, and then click Run. (The Run dialog box appears.)
- Type regedit
Then click OK. (The Registry Editor opens.)
- Navigate to the key:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
- In the right pane, delete any values pertaining to "Windows Update"
- Exit the Registry Editor.
4. Restoring the Internet Explorer settings
- Start Microsoft Internet Explorer.
- Connect to the Internet and go to the page that you want to set as your home page.
- Click Tools > Internet Options.
- In the Home page section of the General tab, click Use Current >OK.
- On the Programs tab, click Reset Web Settings.
Write-up by: Tony Lee
原文請見：http://securityresponse.symantec.com/avcenter/venc/data/adware.cns3721.html
相關報道
金羊網-新快報：殺毒軟件又錯把3721當病毒 3721出面澄清
新快報訊 日前3721又險些被誤認為是病毒。但后據3721方面表示，諾頓病毒清單中的并非為3721產品，僅僅是病毒名稱中含有3721字眼，不會影響用戶正常使用。
據了解，諾頓在10月1日諾頓公司列出了一長串的廣告類病毒名單，其中第十五個“Adware.CNS3721File”可以彈出3721廣告。但3721否認是該病毒文件的制造者。
記者了解到，1999年9月，3721也曾被諾頓認為含有病毒，使得用戶在使用中文網址時，會頻繁彈出病毒報警框。后來3721及時修改了相關的軟件內容應變。
