Backdoor.Slackbot.B

SUMMARY

Backdoor.Slackbot.B is a backdoor Trojan horse that allows a hacker to control your computer using Internet Relay Chat (IRC). Backdoor.Slackbot.B can update itself by checking for newer versions over the Internet.

Behavior

Symptoms

Transmission

Protection

• Virus Definitions (LiveUpdate™ Weekly) October 10, 2001
• Virus Definitions (Intelligent Updater) October 10, 2001

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 backdoor executable file.
• Compromises Security Settings: Allows unauthorized use of the compromised system.

Distribution

• Distribution Level: Low
• Ports: 6667 is the IRC default port. Although this is configurable by the hacker that creates this backdoor.

TECHNICAL DETAILS

Backdoor.Slackbot was created using a special tool; it arrives in the form of a Portable Executable (PE) file. When it is run, it creates a copy of itself as the file \%Windows%wbv.exe.

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

It also adds the value data

%Windows%wbv.exe

to the registry key

HKEY_LOCAL_MACHINESoftwareMicrosoftWindowsCurrentVersionRun

so that the Trojan is run each time that you start Windows.

This backdoor Trojan contains its own Internet Relay Chat (IRC) client. This allows it to connect to an IRC channel that was coded into the Trojan by the hacker who created it. Using the IRC channel, Backdoor.Slackbot listens for commands from the hacker. The commands allow the hacker to perform any of the following actions:

• Manage the installation of the backdoor
• Control the IRC client on the compromised computer
• Dynamically update the installed backdoor
• Send the backdoor to other IRC channels to attempt to compromise more computers
• Download and execute files

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 detected as Backdoor.Slackbot.B and remove the value that it added to the registry.

To delete 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.Slackbot.B.

To edit the registry:

CAUTION: We strongly recommend that you back up the system registry before you make any changes. Incorrect changes to the registry could result in permanent data loss or corrupted files. Please make sure that you modify only the keys that are specified. Please see the document How to back up the Windows registry before you proceed.

1. Click Start, and click Run. The Run dialog box appears.
2. Type regedit and then click OK. The Registry Editor opens.
3. Navigate to the following key:
   
   HKEY_LOCAL_MACHINESoftwareMicrosoftWindowsCurrentVersionRun
   
4. In the right pane, look for a value data that refers to:
   
   %Windows%wbv.exe
   
5. Delete this value if you find it.
6. Click Registry, and then click Exit.