Threat Description



Aliases: Rbot.xt, Backdoor.Win32.Rbot.xt, Rbot
Category: Malware
Type: Backdoor
Platform: W32


RBot represents the large family of backdoors - hacker's remote access tools. These tools allow to contol victims' computers remotely by sending specific commands via IRC channels. Also, these backdoors can steal data and spread to computers vulnerable to exploits.


Automatic action

Once detected, the F-Secure security product will automatically disinfect the suspect file by either deleting it or renaming it.


Detailed instructions for F-Secure security products are available in the documentation found in the Downloads section of our Home - Global site.

You may also refer to the Knowledge Base on the F-Secure Community site for further assistance.

Technical Details

When the backdoor's file is started, it copies itself as 'MSDOS.PIF' file to Windows System folder and then creates the following startup key values in the Registry:

[HKCU\SOFTWARE\Microsoft\Windows\CurrentVersion\Run]  "MSDOS Windows Service" = "MSDOS.PIF"  [HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run]  "MSDOS Windows Service" = "MSDOS.PIF"  [HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\RunServices]  "MSDOS Windows Service" = "MSDOS.PIF"   

When the backdoor is active, it connects to an IRC server, joins a certain channel and acts as a bot there. The backdoor also starts IDENTD server on port 113.

The following IRC server and ports is used by the backdoor:   

The backdoor joins the following password-protected IRC channel:


A hacker can send commands to the bots to control infected computers. Several tasks can be performed, including the following:

* start FTP server  * start TFTP server  * perform ping, SYN, ICMP and UDP flood  * get system information including information about OS, network and drives  * update the backdoor's file from Internet  * operate backdoor's bot (nick change, join/part channels, etc.)  * start remote shell (cmd.exe)  * download and execute files  * enumerate remote shares  * scan and exploit computers vulnerable to exploits   

When spreading, the bot can exploit the following vulnerabilities:

* RPC DCOM (MS03-026) ports 135, 445  * WKSSVC (MS03-049) ports 135, 445   

The bot also tries to connect to IPC$ share, ports 135, 139 and 445 with administrator account and drop a copy of itself in the following directories:

Admin$\\system32  admin$  c$  d$   


F-Secure Anti-Virus detects this malware with the following update:

Detection Type: PC
Database: 2005-08-08_05

Technical Details:Jarkko Turkulainen, August 9th, 2005


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