F-Secure Virus Descriptions : Agent.EO

[Summary] | [Disinfection] | [Detailed Description] | [Detection]

NAME:	Agent.EO
ALIAS:	Backdoor.Win32.Agent.eo, Virus.Win32.Nsag.a

Summary

Agent.EO is a trojan that spies web traffic and modifies infected computers desktop settings. It infects WININET.DLL for activating its spying component. It also downloads and activates PSGuard, which appears to be anti-spyware program.

Disinfection

FSAV is able to remove all infected components and disinfect the modified WININET.DLL. However, a reboot is required for successful WININET.DLL disinfection.

In some cases, FSAV might not be able to disinfected WININET.DLL. On Windows 2000 and XP, File System Protection (FSP) feature might prevent automatic disinfection. In such situations, please follow these steps:

 - Disinfect WININET.DLL manually or wait for FSAV notification for automatic disinfection

 - Verify that WININET.DLL.$DIS file appears in the system folder

 - Add the following value to the registry:
 [HKLM\System\CurrentControlSet\Control\Session Manager]
 "AllowProtectedRenames"=dword:00000001

 - Reboot the system

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Detailed Description

System installation

When the trojan's file is executed, it drops the following files:

 %SysDir%\oleadm.dll
 %SysDir%\wp.bmp
 %WinDir%\uninstIU.exe

'uninstIU.exe' is a simple program that uninstalls the trojan. 'olead.dll' is a spying DLL. It is loaded in every process that imports WININET.DLL (see WININET.DLL infection). 'wp.bmp' is an image that the trojan sets as desktop wallpaper.

The trojan also tries to download and activate PSGuard installation program from psguard.com.

Desktop modifications

The most visible change in the desktop is the wallpaper image which displays a fake error message:

The trojan modifies desktop settings by installing several registry keys. Desktop wallpaper is set with the following registry keys:

 [HKCU\Control Panel\Desktop]
 "Wallpaper" = "%SysDir%\wp.bmp"
 "WallpaperStyle" = "0"

The desktop backgrond color is changed with the following key:

 [HKCU\Control Panel\Colors]
 "Background" = "1 2 172"

The following keys are installed for disabling relevant configuration tabs in windows explorer:

 [HKCU\Software\Microsoft\Windows\CurrentVersion\Policies\System]
 "NoDispAppearancePage" = 1
 "NoDispBackgroundPage" = 1

 [HKCU\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer]
 "NoActiveDesktopChanges" = 1

WININET.DLL infection

The spying component oleadm.dll is activated by installing hooks in Windows system component WININET.DLL. The hook code traps WININET.DLL entry point and exported symbol 'HttpSendRequestA'. When these entry points are called, oleadm.dll is loaded into the address space of process. Infected WININET.DLL is detected as 'Virus.Win32.Nsag.a'.

Web traffic monitoring

When the spying component oleadm.dll is active, it monitors all accessed web pages and sends information to several remote servers.

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Detection

FSAV detects Agent.eo and related components with the following database version:

[FSAV_Database_Version]

Version=2005-06-27_03

Infected WININET.DLL is detected with the following version:

[FSAV_Database_Version]

Version=2005-06-06_02

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Description: Jarkko Turkulainen, Jun 28 2005;

Updated: Jarkko Turkulainen, Aug 26 2005;

F-Secure Corporation