http://www.symantec.com/security_response/writeup.jsp?docid=2003-032416-1326-99&tabid=2 said:
Discovered: March 24, 2003
Updated: February 13, 2007 11:44:50 AM
Type: Trojan Horse
Systems Affected: Windows 2000, Windows 95, Windows 98, Windows Me, Windows NT, Windows Server 2003, Windows XP
When Backdoor.Rsbot runs, it does the following:
1. Copies itself as %System%\Msapp.exe.
Note: %System% is a variable. The Trojan locates the System folder and copies itself to that location. By default, this is C:\Windows\System (Windows 95/98/Me), C:\Winnt\System32 (Windows NT/2000), or C:\Windows\System32 (Windows XP).
2. Adds the value:
"WinApp32" = "%System%\msapp.exe"
to the registry key:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
so that the Trojan runs when you start Windows.
3. Modifies the System.ini file to:
Shell=Explorer.exe msapp.exe
so that the Trojan runs when you start Windows 95/98/Me.
4. Opens a back door on random TCP and UDP ports, which allows a hacker to remotely manipulate the compromised computer and perform actions, such as:
* Stealing system information.
* Performing Denial of Service attacks.
* Uploading and running files.
* Scanning other computer's IP ports, IPC shares.
* Stopping programs from running at startup.
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.
Writeup By: Yana Liu
