Backdoor.Palukka

SUMMARY

Backdoor.Palukka is a backdoor Trojan horse that can give a hacker access to the computer. Like many other backdoor Trojans, Backdoor.Palukka is controlled by the hacker using IRC channels. This particular backdoor Trojan provides a great deal of control over a compromised computer, including file system access and the ability to use the compromised computer in a distributed Denial of Service attack.

Behavior

Symptoms

Transmission

Protection

• Virus Definitions (Intelligent Updater) January 7, 2002

Threat Assessment

Wild

• Wild Level: Low
• Number of Infections: 0 - 49
• Number of Sites: 0 - 2
• Geographical Distribution: Low
• Threat Containment: Easy
• Removal: Easy

Damage

• Damage Level: Medium
• Payload Trigger: Running the Trojan
• Compromises Security Settings: Allows for unauthorized access to the computer.

Distribution

• Distribution Level: Low

TECHNICAL DETAILS

When Backdoor.Palukka is run, it creates a copy of itself as \%Windows%Sysbat.exe.

NOTE: %Windows% is a variable. The worm locates the Windows folder (by default this is C:Windows or C:Winnt) and copies itself to that location.

It may also add a value that refers to Sysbat.exe to one or more of the following registry keys to make sure this file is run on startup:

HKEY_LOCAL_MACHINESoftwareMicrosoftWindowsCurrentVersionRun
HKEY_LOCAL_MACHINESoftwareMicrosoftWindowsCurrentVersionRunOnce
HKEY_LOCAL_MACHINESoftwareMicrosoftWindowsCurrentVersionRunServices
HKEY_LOCAL_MACHINESoftwareMicrosoftWindowsCurrentVersionRunServicesOnce

The hacker can then remotely control the compromised system over IRC channels.

Recommendations

Symantec Security Response encourages all users and administrators to adhere to the following basic security "best practices":

• Turn off and remove unneeded services. By default, many operating systems install auxiliary services that are not critical, such as an FTP server, telnet, and a Web server. These services are avenues of attack. If they are removed, blended threats have less avenues of attack and you have fewer services to maintain through patch updates.
• If a blended threat exploits one or more network services, disable, or block access to, those services until a patch is applied.
• Always keep your patch levels up-to-date, especially on computers that host public services and are accessible through the firewall, such as HTTP, FTP, mail, and DNS services (for example, all Windows-based computers should have the current Service Pack installed.). Additionally, please apply any security updates that are mentioned in this writeup, in trusted Security Bulletins, or on vendor Web sites.
• Enforce a password policy. Complex passwords make it difficult to crack password files on compromised computers. This helps to prevent or limit damage when a computer is compromised.
• Configure your email server to block or remove email that contains file attachments that are commonly used to spread viruses, such as .vbs, .bat, .exe, .pif and .scr files.
• Isolate infected computers quickly to prevent further compromising your organization. Perform a forensic analysis and restore the computers using trusted media.
• Train employees not to open attachments unless they are expecting them. Also, do not execute software that is downloaded from the Internet unless it has been scanned for viruses. Simply visiting a compromised Web site can cause infection if certain browser vulnerabilities are not patched.

REMOVAL

To remove this Trojan, delete files that are detected as Backdoor.Palukka and remove the changes that it made to the registry.

NOTE: If the files are in use by Windows when they are detected by a Norton AntiVirus (NAV) scan, NAV may not be able to delete them. If this is your situation, first follow the instructions in the section To edit the registry; then restart the computer and scan with NAV. (If you prefer, you can restart in DOS mode and then delete the detected files from DOS.)

To remove the Trojan:

1. Run LiveUpdate to make sure that you have the most recent virus definitions.
2. Start Norton AntiVirus (NAV), and make sure that NAV is configured to scan all files. For instructions on how to do this, read the document How to configure Norton AntiVirus to scan all files.
3. Run a full system scan.
4. Delete all files that are detected as Backdoor.Palukka.

To edit the registry:

CAUTION: We strongly recommend that you back up the registry before you make any changes to it. Incorrect changes to the registry can result in permanent data loss or corrupted files. Modify only the keys that are specified. Read the document How to back up the Windows registry for instructions.

1. Click Start, and click Run. The Run dialog box appears.
2. Type regedit and then click OK. The Registry Editor opens.
3. For each of the following keys:
   
   HKEY_LOCAL_MACHINESoftwareMicrosoftWindowsCurrentVersionRun
   HKEY_LOCAL_MACHINESoftwareMicrosoftWindowsCurrentVersionRunOnce
   HKEY_LOCAL_MACHINESoftwareMicrosoftWindowsCurrentVersionRunServices
   HKEY_LOCAL_MACHINESoftwareMicrosoftWindowsCurrentVersionRunServicesOnce
   
   look in the right pane for any value that refers to:
   
   Sysbat.exe
   
   and delete it.
4. Exit the Registry Editor.