2003-08-12 -
Symantec Security Response has identified a new Level 3 worm in the wild -- W32.Blaster.Worm -- that is exploiting the Microsoft DCOM RPC Interface Buffer Overrun vulnerability. Due to the high number of users impacted by this vulnerability, Symantec has raised the ThreatCon* to a Level 3. Systems affected include Microsoft IIS, Windows 2000, Windows XP and Windows NT.
W32.Blaster.Worm uses the DCOM MSRPC vulnerability to compromise a remote system. It attempts to connect to TCP port 4444 after the attack and then uses tftp to retrieve and install a copy of itself onto the infected system.
When the W32.Blaster.Worm is executed, it will do the following:
1. Adds the value: "windows auto update"="msblast.exe" to the registry key: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
so that the worm runs when you start Windows.
2. Send data on TCP port 135 that may exploit the DCOM RPC vulnerability to allow the following actions to occur on vulnerable machine: the worm will be downloaded and will run using the program tftp.
Through analysis of the worm, Symantec has determined that it contains code to launch a Denial-of-Service attack against windowsupdate.com during a specific time period. The worm will launch a Denial-of-Service attack after August 15th through the end of the year, every year.
Through Symantec's DeepSight Threat Management System, Symantec has identified that over 57,000 systems have been infected and are currently launching probes against Port 135. This number has grown exponentially in the last 24 hours as the average was 1000 - 2000 as of August 10th. Symantec's Managed Security Services reports that W32.Blaster.Worm is propagating at a rate of roughly 20% that of the Slammer worm, in terms of instances of infection (unique IP addresses) per hour passing through our client's security devices.
Microsoft issued a patch for this vulnerability on July 16th. Symantec Security Response strongly encourages users to patch systems. The patch is available at http://www.microsoft.com/technet/treeview/default.asp?url=/technet/security/bulletin/MS03-026.asp
More information on this worm and how to delete and scan for infected files can be found on the Symantec Security Response website - http://securityresponse.symantec.com/avcenter/venc/data/w32.blaster.worm.html
*ThreatCon is an instantaneous measurement of global threat exposure. For definitions, please visit https://tms.symantec.com/threatCon_Def.asp
