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Rootkit:W32/TDSS.gen!A

First posted on 25 March 2010.
Source: SecurityHome

Aliases :

Rootkit:W32/TDSS.gen!A is also known as Trojan:WinNT/Alureon.C (Microsoft).

Explanation :

A program or set of programs which hides itself by subverting or evading the computer's security mechanisms, then allows remote users to secretly control the computer's operating system.

Additional DetailsRootkit:W32/TDSS.gen!A is a Generic Detection that identifies malware attempting to conceal the existence of certain malicious files. The purpose of this rootkit is to maintain its launchpoints and keep them and the files hidden during runtime.

About Generic Detections

Unlike signature or single-file detections, a Generic Detection does not identify a unique or individual malicious program. Instead, a Generic Detection looks for broadly applicable code or behavior characteristics that indicate a file as potentially malicious, so that a single Generic Detection can efficiently identify dozens, or even hundreds of malware.

Installation

The rootkit will set hooks to the following APIs:
€ IofCallDriver € IofCompleteRequest € NtFlushInstructionCache € NtQueryValueKey € NtEnumerateKey The hooks 'NtQueryValueKey' and 'NtEnumerateKey' render users unable to see the registry entries created by the rootkit.

Then, it creates the following registry entries:
€ HKLM\SOFTWARE\gaopdx\disallowed € HKLM\SOFTWARE\gaopdx\injector € HKLM\SOFTWARE\gaopdx\trusted € HKLM\SOFTWARE\gaopdx\connections € HKLM\SYSTEM\CurrentControlSet\Services\gaopdxserv.sys € HKLM\SYSTEM\ControlSet001\Services\gaopdxserv.sys € HKLM\SYSTEM\ControlSet002\Services\gaopdxserv.sys € HKLM\SYSTEM\CurrentControlSet\Services\sharedaccess\Parameters\Firewallpolicy\publicprofile
enablefirewall : 0 € HKLM\SYSTEM\CurrentControlSet\Services\Sharedaccess\Parameters\Firewallpolicy\domainprofile
enablefirewall : 0 € HKLM\SYSTEM\CurrentControlSet\Services\Sharedaccess\Parameters\Firewallpolicy\standardprofile
enablefirewall : 0
And drops a driver with a random filename to system32\drivers\folder
€ gaopdx[random].sys
A DLL is then dropped to the system32\ folder and is kept hidden
€ gaopdx[random].dll
From that point on, any filename that contains the word 'gaopdx' at the beginning of its name will be hidden.

Activity

The rootkit uses Notify Routines to monitor and prevent the following files from running:
€ avp.exe € klif.sys € mrt.exe € spybotsd.exe € saskutil.sys € sasenum.sys € szkg.sys € szserver.exe
The rootkit monitors all processes and keeps the registry keys up-to-date all the time, making it impossible to get them removed. If 'Ntdll.dll' and 'Kernel32.dll' gets loaded in, it tries to inject the payload DLL if the process-name is in the injector list.

Then, it will post encrypted information to remote server with command:
€ POST /extrax.php HTTP/1.0

Last update 25 March 2010

 

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