GEN:SID 1:2495
Message NETBIOS SMB DCEPRC ORPCThis request flood attempt
Summary This event is generated when an attempt is made to exploit a known
vulnerability in the Microsoft RPC service.
Impact Denial of Service (DoS). Possible execution of arbitrary code leading to
unauthorized remote access to the victim host.
Detailed Information It may be possible for an attacker to cause a DoS condition in the
Microsoft RPC service when multiple simultaneous requests are made to a
vulnerable host. This can lead to an exhaustion of system resources
causing the DoS.
Affected Systems Windows systems running RPC services
Attack Scenarios An attacker may attempt to bind to the RPC service many times in an
attempt to cause the DoS condition to occur.
Ease of Attack Difficult.
Corrective Action Block access to RPC ports 135, 139 and 445 for both TCP and UDP
protocols from external sources using a packet filtering firewall.

Apply the appropriate vendor supplied patches
Additional References  
Rule References bugtraq: 8811
cve: 2003-0813
nessus: 12206
url: www.microsoft.com/technet/security/bulletin/MS04-011.mspx