Trojan.Macur

SUMMARY

Trojan.Macur is a Trojan horse that attempts to disguise itself as a .jpg file.

Protection

• Virus Definitions (LiveUpdate™ Weekly) December 4, 2002
• Virus Definitions (Intelligent Updater) December 2, 2002

TECHNICAL DETAILS

When Trojan.Macur runs, it performs the following actions:

First, the Trojan locates the current folder and the Windows installation folder. If the third, seventh, and eighth characters of these two folders are different, the Trojan displays this message:



Next, the Trojan copies itself as %windir%Pic.exe and adds the following line to the Win.ini file:

load=pic.exe

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

Finally, it attempts to create 1,506 directories in the %windir% folder. The names of these folders are

0
00
000
.
.
.
000000...000
1
11
111
.
.
.
111111...111
.
.
.
5
55
555
.
.
.
555555...555

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

NOTE: These instructions are for all current and recent Symantec antivirus products, including the Symantec AntiVirus and Norton AntiVirus product lines.

1. Update the virus definitions.
2. Run a full system scan, and delete all files that are detected as Trojan.Macur.
3. (Windows 95/98/Me only): Delete the line
   
   load=pic.exe
   
   from the Win.ini file
4. Delete all folders that Trojan.Macur created.

For details on how to do this, read the following instructions.

To update the virus definitions:
All virus definitions receive full quality assurance testing by Symantec Security Response before being posted to our servers. There are two ways to obtain the most recent virus definitions:

• Run LiveUpdate, which is the easiest way to obtain virus definitions. These virus definitions are posted to the LiveUpdate servers once each week (usually Wednesdays) unless there is a major virus outbreak. To determine whether definitions for this threat are available by LiveUpdate, look at the Virus Definitions (LiveUpdate) line at the top of this write-up.
• Download the definitions using the Intelligent Updater. Intelligent Updater virus definitions are posted on U.S. business days (Monday through Friday). They must be downloaded from the Symantec Security Response Web site and installed manually. To determine whether definitions for this threat are available by the Intelligent Updater, look at the Virus Definitions (Intelligent Updater) line at the top of this write-up.
  
  Intelligent Updater virus definitions are available here. For detailed instructions on how to download and install the Intelligent Updater virus definitions from the Symantec Security Response Web site, click here.

To scan for and delete the infected files:

1. Start your Symantec antivirus program, and make sure that it is configured to scan all files.
   • Norton AntiVirus consumer products: Read the document How to configure Norton AntiVirus to scan all files.
   • Symantec enterprise antivirus products: Read the document How to verify a Symantec Corporate antivirus product is set to scan All Files.
2. Run a full system scan.
3. If any files are detected as infected with Trojan.Macur, click Delete.

To edit the Win.ini file:
This is necessary only on Windows 95/98/Me-based computers

NOTE (for Windows Me users only): Due to the file-protection process in Windows Me, a backup copy of the file that you are about to edit exists in the C:WindowsRecent folder. Symantec recommends that you delete this file before you continue with the steps in this section. To do this using Windows Explorer, go to C:WindowsRecent, and in the right pane select the Win.ini file and delete it. It will be regenerated as a copy of the file that you are about to edit when you save your changes to that file.

1. Click Start, and click Run.
2. Type the following, and then click OK.
   
   edit c:windowswin.ini
   
   The MS-DOS Editor opens.
   
   NOTE: If Windows is installed in a different location, make the appropriate path substitution.
   
3. In the [windows] section of the file, look for an entry similar to the following:
   
   load=pic.exe
   
   If it exists, select the entire line. Be sure that you have not selected any other text, and then press Delete.
4. Click File, and click Save.
5. Click File, and click Exit.

To delete all folders that Trojan.Macur created:
Using Windows Explorer, locate all subfolders in the %windir% folder whose name consists of a number. After making sure that it is one that was created by the Trojan, and not a legitimate folder, delete it.