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F-Secure Malware Information Pages: Worm:W32/Agent.T
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Summary
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| Worm:W32/Agent.T copies itself to the Windows folder and downloads files from several websites and executes them. |
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Disinfection
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Automatic Disinfection
Usually standalone malware (backdoors, worms, trojans, etc.) is automatically removed by F-Secure Anti-Virus (FSAV) starting from version 5.40. Malware files get automatically renamed by FSAV, so they can not be started any more. In some rare cases, when automatic disinfection is not possible, a user can select disinfection action by themselves to make FSAV rename or delete an infected file. In some special cases, it is recommended to use specific disinfection tools provided by F-Secure. They can be downloaded from our ftp site:
ftp://ftp.f-secure.com/anti-virus/tools/
F-Secure Anti-Virus can be purchased from our webshop or from our authorized distributors. A trial version F-Secure Anti-Virus, limited to 30 days, can be downloaded from our website:
http://www.f-secure.com/download-purchase/
All the latest versions of FSAV can download anti-virus database updates automatically. However, these updates can be also downloaded and installed manually from our web or ftp sites:
http://www.f-secure.com/download-purchase/updates.shtml
Manual Disinfection
To manually disinfect standalone malware (backdoors, worms, trojans, etc.) it's usually enough to delete all infected files from a computer and to restart it. Active malware files are usually locked by operating system so different disinfection approaches are required for different operating systems.
Please note that manual disinfection is a risky process, so it is recommended only for advanced users.
If Windows 95, 98 and ME operating system is used, it is recommended to restart a computer from a bootable system diskette and to delete an infected file from command prompt. For example if a malicious file named ABC.EXE is located in Windows folder, it is usually enough to type the following command at command prompt:
DEL C:\WINDOWS\ABC.EXE
and to press Enter. After that an infected file will be gone. If Windows NT, 2000 or XP is used, a malicious file has to be renamed with a different extension (for example .VIR) and then a system has to be restarted. After restart a renamed malicious file will no longer be active and it can be easily deleted manually.
Malware Disinfection Tools
F-Secure provides disinfection tools for certain malware. These tools can be downloaded from this webpage:
http://www.f-secure.com/download-purchase/tools.shtml
ftp://ftp.f-secure.com/anti-virus/tools/
Windows System Restore Issues
If Windows ME or XP is used, it is recommended to disable System Restore feature of these operating systems to prevent a computer from re-infection by an already removed malware. The fact is that System Restore feature of these operating systems might save an infected file into the special folder and copy it back to a hard drive it every time it's been renamed or deleted by F-Secure Anti-Virus or by a user. Instructions on how to disable System Restore feature are here:
Windows ME:
http://www.f-secure.com/v-descs/sfc_dis.shtml
Windows XP:
http://www.f-secure.com/v-descs/sfc_dis1.shtml
It is recommended to re-enable System Restore after disinfection in order to restore stable system configuration in the future, if any crash or incompatibility issue occurs.
Failed Disinfection
In some cases F-Secure Anti-Virus might not disinfect a system automatically. In this case please visit our Support pages:
http://support.f-secure.com/enu/home/virusproblem/howtoclean/ |
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Detailed Description
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Agent.T is malware that may drop several copies of itself onto the system and downloads other additional malware from the Internet.
Upon execution, it drops the following files:
- %windir%\yqqty.exe - A copy of itself.
It modifies the following autostart registry entry to enable its automatic execution every system boot-up:
- [HKLM\Software\Microsoft\Windows NT\CurrentVersion\Winlogon]
Userinit=%windir%\system32\userinit.exe,%windir%\yqqty.exe
Note: The default value is Userinit=%windir%\system32\userinit.exe
It may drop a copy of itself to several drives. The Autorun.inf file, which is a configuration file used to automatically execute the malware when a directory or drive is being opened, is also dropped together with the main executable file.
Agent.T also downloads the following files from the Internet:
- http://www.sinavip.net/A[REMOVED].asp
- http://www.sinavip.net/L[REMOVED].txt
It then saves the files to the Windows directory using the following filenames:
One of the text files contains the following download sites:
- http://www.aame.cn/k[REMOVED].rar
- http://www.aame.cn/c[REMOVED].rar
The downloaded files are also trojan-downloaders that are now detected as Trojan-Downloader:W32/Small.EJW and Trojan-Downloader:W32/Small.ELM. |
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Detection
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F-Secure Anti-Virus detects this malware with the following updates: [FSAV_Database_Version] Version = 2007-03-22_07.
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F-Secure Corporation |
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Last Modified: April 05, 2007
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