Trojan.Mos

SUMMARY

Trojan.Mos is a Symbian Series 60 Trojan horse that sends a message using the Short Message Service (SMS) to a high-cost phone number.

The program is a clone of a popular game known as Mosquitos.

Protection

• Virus Definitions (LiveUpdate™ Weekly) August 11, 2004
• Virus Definitions (Intelligent Updater) August 10, 2004

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: Sends an SMS to a high-cost phone number.

Distribution

• Distribution Level: Low

TECHNICAL DETAILS

When Trojan.Mos is executed, it performs the following actions:

1. Copies itself to systemappsMosquitosMosquitos.app.
   
   
2. Sends an SMS message to a high-cost phone number.
   
   
3. Starts a game that is similar to a popular game known as Mosquitos produced by Ojom.
   
   The version of the game that contains the Trojan will display the following screen while the game loads:
   
   
   

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 Trojan.Mos:

1. Install a file manager program on the phone.
2. Enable the option to view the files in the system folder.
3. Search the drives, A through Y, for the systemappsMosquitos folder.
4. Delete the Mosquitos folder.