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
原文请见：http://securityresponse.symantec.com/avcenter/venc/data/adware.cns3721.html
相关报道
金羊网-新快报：杀毒软件又错把3721当病毒 3721出面澄清
新快报讯 日前3721又险些被误认为是病毒。但后据3721方面表示，诺顿病毒清单中的并非为3721产品，仅仅是病毒名称中含有3721字眼，不会影响用户正常使用。
据了解，诺顿在10月1日诺顿公司列出了一长串的广告类病毒名单，其中第十五个“Adware.CNS3721File”可以弹出3721广告。但3721否认是该病毒文件的制造者。
记者了解到，1999年9月，3721也曾被诺顿认为含有病毒，使得用户在使用中文网址时，会频繁弹出病毒报警框。后来3721及时修改了相关的软件内容应变。
