F-Secure Virus Descriptions : RPC

NAME:	RPC
ALIAS:	Exploit.Win32.Autorooter, RPC-1, Cirebot, Downloader-DM

A set of files using a security vulnerability in Windows operating system was found around 19:00 GMT on saturday 2nd of August, 2003.

Scenario looked bad in the beginning, as the package contained files with names such as rpc.exe and worm.exe.

After detailed analysis, we can confirm that this is not a worm at all. It does not even attempt to spread further from affected hosts.

The vulnerability being used here is MS03-026, "Buffer Overrun In RPC Interface". http://www.microsoft.com/technet/security/bulletin/MS03-026.asp This vulnerability was discovered on July 16th, 2003.

This program will create these files to local hard drive:

  rpc.exe
  rpctest.exe
  tftpd.exe
  dcomx.exe
  lolx.exe
  worm.exe

Rundown of the files:

Worm.exe is a self-extracting archive that will create rpc.exe, rpctest.exe and tftp.exe.

Tftp.exe is a normal tftp server utility.

Rpctest.exe and rpc.exe are part of autorooter.zip tool, released around 30th of June. Rpctest.exe uses the known RPC exploit to spawn a remote shell which listens at TCP port 57005. It contains the text "USE THE FORZ LUKE!" Rpc.exe contains text "rpc autorooter by ERIC". These programs are written which Microsoft Visual Basic.

Dcomx.exe and lolx.exe are based on older backdoors and are already detected by F-Secure Anti-Virus as variants of "Sdbot". For more information on Sdbot irc-based backdoors, see: http://www.f-secure.fi/v-descs/sdbot.shtml

So, all files are accounted for. There's no worm here. If somebody would be sitting at the IRC channel and giving commands manually to affected machines, he could get the tool propogated from one machine to another. But that wouldn't be automatic.

We recommend all users apply the Microsoft patch (available from the above Microsoft link). Also, blocking TCP ports 135, 139 and 445 in your local firewall will help. F-Secure Distributed Firewall blocks these by default.

[Analysis: Gergo and Mikko, F-Secure Corp, 2nd of August 2003]