The warnings about an imminent wave of attacks on the RPC vulnerability in Windows continued on Thursday as the CERT Coordination Center issued an advisory detailing the tools that crackers are using to exploit the flaw.
Officials at CERT said that they have seen several different attack tools for this vulnerability and that the exploits are currently being refined and tuned for automated exploitation of the weakness. This vulnerability is considered especially dangerous because it affects every currently supported version of Windows and enables attackers to run their own code on compromised machines.
At least one of the known exploits circulating on the Internet attempts to connect to TCP port 135 and installs a back door on the machine once it does connect. Other versions of the tool use port 4444 to connect and still others allow the attacker to specify the port of his choice, according to CERTs bulletin.
Exploit code for this vulnerability has been posted on at least one security Web site and is likely available in several other places, as well.
Reports have also surfaced that machines that have the patch for this vulnerability installed are still vulnerable to a denial-of-service (DoS) attack against the same flaw. Thor Larholm, a senior security researcher at PivX Solutions LLC in Newport Beach, Calif., said in a message to the BugTraq security mailing list that he has confirmed that a machine running Windows 2000 Service Pack 4 with the RPC patch installed is vulnerable to the DoS attack.
CERT said in its bulletin that it is tracking the DoS issue as a separate vulnerability. Microsoft has yet to address this problem with a new or updated patch.
The RPC vulnerability is found in a portion of the Remote Procedure Call protocol that handles message exchanges over TCP/IP. The vulnerability, which arises because of incorrect handling of error messages, affects a particular Distributed Component Object Model interface with RPC.
The interface handles DCOM object activation requests sent by client machines to the server, Microsoft said in its bulletin. A successful exploitation of this flaw would give an attacker the ability to run code with local system privileges on the compromised machine. This would give the attacker complete control of the system.
The prevalence of the RPC flaw has security experts and government officials concerned about the possibility of someone either writing a worm to exploit the weakness or a rash of individual attacks against vulnerable machines.
"Because of the significant percentage of Internet-connected computers running Windows operating systems and using high speed connections the potential exists for a worm or virus to propagate rapidly across the Internet carrying payloads that might exploit other known vulnerabilities in switching devices, routers, or servers," according to an advisory published by the National Infrastructure Protection Center.