Abstract:
A method and apparatus for enabling a network security service and network security infrastructure to detect, identify, mitigate, neutralize, and disable worms through distributed worm probes that can be linked to centralized monitoring systems for emergency response process is disclosed. The worm probes track packets with destination unreachable errors on a per source IP address basis. In one embodiment, when the number of such errors exceeds a predefined local threshold, e.g., within a predefined local time period at a worm probe, the count of such errors as well as the source IP address will be sent to all other worm probes in the network as an alert. When the number of such errors exceeds a predefined global threshold, e.g., within a predefined global time period, traffic from the endpoint device with the identified source IP address will be blocked to prevent that endpoint device from spreading worms further.

Description:
[0001]     The present invention relates generally to communication networks and, more particularly, to a method and apparatus for identifying and disabling worms, e.g., TCP/IP worms, in packet networks, e.g. Internet Protocol (IP) networks.  
       BACKGROUND OF THE INVENTION  
       [0002]     Small companies and home PC users believe that their systems are not intended targets to a serious hacker because a serious hacker would be more interested in more critical infrastructure and systems. It is true that even after spending considerable effort, a skilled hacker may not be able to break into these non-critical systems. However, skilled hackers are not the major threat, and the biggest threat comes from internet worms e.g., TCP/IP worms, which are in worm infected systems connected to networks, constantly and automatically attempting to penetrate computer systems to infect these systems and to turn them into same attacking machines. A TCP/IP worm is software which is developed by skilled hackers. After hackers manually infect a TCP/IP worm into an infect-able system on the internet, this TCP/IP worm infected system start to send out billions of TCP/IP worm IP packets to try to penetrate millions of computer systems on the internet. An infect-able system receives such TCP/IP worm IP packets will be infected automatically. In turn, it starts to send out billions of same TCP/IP worm IP packets to try to penetrate other systems. As a domino effect, the more infect-able systems receive TCP/IP worm IP packets, the more TCP/IP worm infected systems and the more TCP/IP worm IP packets to be send out. This type of penetration attack is performed automatically and takes virtually no human hacking effort to attack millions of potential victims. Anyone with a firewall on the Internet feels the steady background IP packets from these TCP/IP worm attacks. If a system connects to the Internet, chances are that every few minutes, a TCP/IP worm, somewhere on the Internet, may attempt to penetrate this system. The TCP/IP worm trying to penetrate this system may not be launched by a skilled hacker and may not spend a significant of time and effort. If the worm succeeds in breaking into this system, it is accomplished automatically by chance.  
         [0003]     With all kinds of new TCP/IP worms that are being created to attack thousands of different vulnerabilities against millions of systems on the Internet, the chance that some of the worms will succeed in finding a combination of vulnerabilities which can penetrate millions of computer systems and turns them into TCP/IP worm attacking machines within hours is quite high. It has been observed that significant damages can be inflicted, e.g., through denial of services caused by a huge volume of network traffic that is generated by millions of TCP/IP worm infected computer systems sending out attacking worm IP packets. If a TCP/IP worm infected system is connected to a company internal network via wired Local Area Network (LAN), wireless LAN, Virtual Private Network (VPN), dial up network, or any other methods, it will attack the corporate internal network in the same way, thereby causing significant harm to the company&#39;s internal network.  
         [0004]     All IP network service providers are facing this serious problem. This includes all top tier internet service providers, large corporations, network outsourcing service providers, as well as many small companies. TCP/IP worms are serious problems that need to be addressed immediately.  
         [0005]     Therefore, a need exists for a method and apparatus for identifying and disabling worms, e.g., TCP/IP worms, in any IP network.  
       SUMMARY OF THE INVENTION  
       [0006]     In one embodiment, the present invention enables a network security service and network security infrastructure to detect, identify, mitigate, neutralize, and disable worms, e.g., TCP/IP worms, through distributed worm probes that can be linked to centralized monitoring systems for emergency response process. The worm probes track packets with destination unreachable errors on a per possible worm originating source IP address count basis to multiple destination IP addresses, and track all IP packets on a per possible worm originating source IP address count basis to multiple destination IANA (Internet Assigned Numbers Authority) reserved IP addresses. When the number of such counts of possible worm originating source IP address exceeds a predefined local threshold within local predefined time period at a worm probe, the counts of such errors as well as the possible worm originating source IP address will be sent to all other worm probes in the network as an alert. When the number of such counts of possible worm originating source IP address exceeds a predefined global threshold within predefined global time period, traffic from the endpoint device with the identified worm originating source IP address will be blocked to prevent that endpoint device from spreading worms further. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]     The teaching of the present invention can be readily understood by considering the following detailed description in conjunction with the accompanying drawings, in which:  
         [0008]      FIG. 1  illustrates an exemplary global corporate IP network related to the present invention;  
         [0009]      FIG. 2  illustrates a flowchart of the main method for identifying and disabling TCP/IP worm infected systems in an IP network of the present invention;  
         [0010]      FIG. 3  illustrates a flowchart of sub-method “Possible worm IP address table periodical clearing” for identifying and disabling TCP/IP worm infected systems of the present invention;  
         [0011]      FIG. 4  illustrates a flowchart of sub-method “Add possible worm” for identifying and disabling TCP/IP worm infected systems of the present invention;  
         [0012]      FIG. 5  illustrates a flowchart of sub-method “Receive Global Change” for identifying and disabling TCP/IP worm infected systems of the present invention;  
         [0013]      FIG. 6  illustrates the Internet Control Message Protocol type 3 packet format related to the present invention;  
         [0014]      FIG. 7  illustrates a high level components diagram of a general purpose computer suitable for use in performing the functions described herein;  
         [0015]      FIG. 8  illustrates an exemplary data structure of the Local Table of the present invention; and  
         [0016]      FIG. 9  illustrates an exemplary data structure of the Global Table of the present invention. 
     
    
       [0017]     To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures.  
       DETAILED DESCRIPTION  
       [0018]     Worms, e.g., Transport Control Protocol/Internet Protocol (TCP/IP) worms not only damage vulnerable computer systems on the internet, but they also generate a large volume of network traffic which causes network Denial of Service (DOS) attack.  
         [0019]     A worm, e.g., a TCP/IP worm, is a self-replicating computer program, similar to a computer virus. A virus attaches itself to, and becomes part of, another executable program; however, a worm is self-contained and does not need to be part of another program to propagate itself. They are often designed to exploit the data transmission capabilities such as the TCP/IP protocol found on many computers. Major TCP/IP worm attacks include infamous Code Red, Slapper, and SQUSlammer, that causes serious impacts on global networks in recent years. The United States Government announced “The National Strategy to Secure Cyberspace” initiative and described TCP/IP worms as the cause of billions of dollars in damage that served as a wake-up call for a nation that had become dependent on computer networks.  
         [0020]     In all companies and many home networks, there are computers connected to either the internet or company intranet. So far, there is no effective way to detect new TCP/IP worms until they attack thousands of computers and turn these computers into TCP/IP worm attacking machines. Namely, the network security industry, including internet and computer security companies, have failed to provide effective methods or products quickly enough to identify and mitigate new TCP/IP worms which have unknown signatures and strike and take down major internet hub nodes.  
         [0021]     An Intel Pentium III 500 MHz PC with a gigabit Ethernet Network Interface Card (NIC) infected with a worm, e.g., the SQUSlammer worm, can produce over 100,000 packet/second or 300 megabit/second (Mbps) of traffic. The infected computer randomly chooses target IP addresses to attempt to break into computers associated with these IP addresses. This means that a single machine with the right Internet connection can attack the entire Internet in 12 hours. If one computer system with a 10/100 Mbps NIC card can be penetrated and turned into a TCP/IP worm infected machine, it will immediately consume all the bandwidth of the 10/100 Mbps network and the outgoing direction bandwidth of a Wide Area Network (WAN) connection using T1 (1.5 Mbps) or T3 (45 Mbps) interface connections. With a couple of high end systems in a data center infected with a TCP/IP worm, they can easily consume all the bandwidth in the outgoing direction of an OC3 (155 mbps) or even an OC12 (622 mbps) WAN interface connections. In the incoming direction of those congested WAN interface, almost 100% of the IP packets will fail to reach the network on which the infected computer system resides. Unless the infected computer system is physically shutdown or disconnected from network, the only remote IP traffic control to mitigate this problem is to apply a filter to the routers or switches connected to the WAN connection. Even today, new DOS attacks caused by TCP/IP worms which create congestions at WAN connections are almost unavoidable because there are too many new variants of TCP/IP worms being created to constantly and automatically attack thousands of different vulnerabilities against millions of computer systems on the TCP/IP network.  
         [0022]      FIG. 1  illustrates an exemplary global IP network related to the present invention. Namely,  FIG. 1  illustrates an example network, e.g., a packet network such as an IP (Internet Protocol) network related to the present invention. Exemplary packet networks include internet protocol (IP) networks, asynchronous transfer mode (ATM) networks, frame-relay networks, and the like. An IP network is broadly defined as a network that uses Internet Protocol to exchange data packets.  
         [0023]     To illustrate, in  FIG. 1 , global corporate IP network  110  is connected to the Internet  120  via router  131  and router  132 . Global corporate IP network may include locations in Asia Pacific, Europe, United States, Canada, and Latin America. Worm probes  111 ,  112 , and  113  are deployed at key locations in various countries to detect worm, e.g., TCP/IP worm, related activities. Table  140  shows exemplary suspicious global worm activity counts and their associated possible worm originating source IP address. When the suspicious worm activity counts exceed a predefined global threshold within a predefined time period, the router or switch closest to the source IP address originating the suspicious worm activities will be informed to block all traffic from the machine with that particular worm originating source IP address, thereby preventing the TCP/IP worms from spreading and blocking worm IP packets which have huge volume to cause the network traffic jam.  
         [0024]     The theory behind the present invention is that TCP/IP worm infected system sends out worm packets to randomly generated destination IP addresses which include IANA reserved IP addresses and many IP addresses without a live system. For example, the whole IP version 4 (IPv4) has an address space of 4,294,967,296 IP addresses. This includes private IP addresses, broadcasting IP addresses, multicasting IP addresses, loopback IP addresses and Internet Assigned Numbers Authority (IANA) reserved IP addresses. Also, for those IP addresses with live systems, not every IP address has protocols or ports in service on which a worm is penetrating. For example, a Simple Mail Transfer Protocol (SMTP) server may not have the TCP port number  80  open. Also, even if the live system using an IP address has a particular port open, it may not have a vulnerability on which a worm can penetrate. For example, a known worm called “Code Red Worm” can only penetrate Microsoft Internet Information Server (IIS) web server with “dot dot backslash” type vulnerabilities. Therefore, before a worm infected system penetrates another computer system, it should have already sent many worm packets to IANA reserved IP addresses, to many IP addresses without live systems, to systems which do not have certain protocols and ports in service and left behind trails of IP traffic associated with the worm attack in the IP network because by default the IP network devices replies to the worm system with an ICMP unreachable packet, such as ICMP type 3 packets that have code 0, 1, 2 or 3, to inform worm system if an IP address is not routable, or it does not have a live system, or the system does not have certain protocols and ports in service.  
         [0025]     If a special worm probe device uses the trails of these ICMP unreachable packets, it can immediately identify the system that receives these ICMP unreachable packets coming from multiple systems is infected with a TCP/IP worm or is performing IP address scans in the IP network. If such a system is not a known authorized IP address scan system, the special worm probe device can automatically communicate with firewalls, routers, switches and hubs in the IP network to block traffic originated from the worm infected computer system or command the worm infected computer system to be shutdown. In this manner, the worm can be neutralized and disabled automatically within seconds even if this worm is a new variant unknown features, such as what port it is attempting to penetrate, what protocol it is attempting to penetrate, what Operating System (OS) it is attempting to penetrate, what application it is attempting to penetrate, what vulnerability it is attempting to penetrate, or what worm signature it possesses etc. As long as the suspected system is sending worm packets to IANA reserved IP addresses, to IP addresses without live systems, to systems without certain protocols and ports in service, it will leave behind trails of ICMP unreachable traffic coming from multiple systems.  
         [0026]     The mathematical statistics behind the present invention is to use L, M, N, X and Y as follows: 
        L is the total number of IP addresses available in a network cloud;     M is the total number of IP addresses with live systems in a network cloud;     N is total number of IP addresses of which a worm can penetrate within a network cloud;     X is the average number of IP addresses within this network cloud attacked by a worm before a computer system is penetrated; and     Y is the average number of IP unreachable addresses attacked by the worm that leaves behind the attack trails within this network cloud before a computer system is penetrated.        
 
         [0032]     In one embodiment, X=(L/N)−1 and Y=(L−M)/N. For example, in a class A subnet with prefix 9.x.x.x, 100,000 IP addresses are used by computer systems, and half of them use Windows OS and half of them use Unix or other OS. Also, out of the 100,000 computer systems, 50,000 IP addresses of computer systems use Windows OS; furthermore, half of these 50,000 systems, 25,000, have vulnerability which allows a worm to penetrate and infect these systems. In addition, 100,000 more IP addresses are used by network devices, such as routers, switches, hubs and etc. A class A IP subnetwork has a total of 16,777,216 valid IP addresses. Within this example, there are a total of 200,000 IP addresses with live systems, and 100,000 of them for computer systems and 100,000 of them for networking devices. Also, out of the 50,000 Windows OS machines, there are 25,000 IP addresses of Windows OS systems which could be penetrated and infected with worms. Now, assume someone releases a new worm in the internet. This worm may randomly penetrate a multi-home computer system A which has one interface to subnet 9.x.x.x. Based on statistics, before system A can penetrate another system, say B, in subnet 9.x.x.x, system A will attack on average 670 IP addresses within subnet 9.x.x.x, e.g. X=(16777216/25000)−1=670. System A also creates  663  trails of unreachable IP address attack traffic on average, e.g. Y=(16777216-200000)/25000=663. If some worm probe devices of the present invention are placed within subnet 9.x.x.x, they will be able to detect some of these trails of worm attacks to unreachable IP address and identify system A as an infected system before it can penetrate another system B based on the average number of attempts originated by system A. Within seconds, these worm probe devices can automatically communicate to firewalls, routers, switches and hubs to block traffic originated from system A or command system A to be shutdown. Since 663 is only the average number of attempts before another system is infected based on statistics, system A may actually penetrate system B before it can be identified as an infected system. In that case, as soon as system A is identified, all traffic originated from it will be blocked. Furthermore, if system B is infected, it will be identified and its traffic blocked using the same method by these worm probe devices. Based on the described mathematics, one can see that in order to obtain a large number of Y so that the trails left behind by the attacks to unreachable IP address created by a worm infected system can be detected quickly before the worm penetrate another system, the ratio of available IP addresses vs. IP addresses with live system should be large enough. The higher the ratio, the less likely to let worm system A to penetrate infect-able system B. The lowest ratio which disables worm system A before it penetrates worm infect-able system B is about 20:1 for Code Red worm in 10 Mbps network with one tenth of systems are infect-able systems. When the ratio becomes very low, such as 2:1, the worm probe devices are still able to identify and disable worm system A. The difference between a high ratio and a low ratio is that in a high ratio scenario, worm infect-able system B may not be penetrated while in a low ratio scenario, worm infect-able system B may be penetrated and becomes another worm infected system attacking other infect-able systems.  
         [0033]      FIG. 2  illustrates a flowchart of a main method for identifying and disabling TCP/IP worm infected systems of the present invention. Method  200  starts in step  210  and proceeds to step  215 . Note that worm probe devices are deployed strategically in heavy traffic IP nodes. Key locations include, but are not limited to, most of LAN IP subnet and main traffic aggregation hubs or exchange points with heavy IP traffic load in the network, such as border router, firewall, proxy, VPN concentrator, Intrusion Detection System (IDS) and Intrusion Prevention System (IPS) segments. An IDS is a system that alerts the user to the presence of an intrusion on the network through network traffic analysis techniques. An IPS is a system that exercises access control to protect computers from exploitation from unauthorized users.  
         [0034]     In step  215 , method  200  uses the worm probe devices to listen to all IP packets, e.g., TCP, UDP, ICMP and other protocols IP packets that pass by a worm probe NIC card on the network. In step  220 , method  200  checks if the destination IP address of an IP packet is in the Internet Assigned Numbers Authority (IANA) reserved IP address space. Note that TCP/IP worms attack potential target machines using randomly generated IP addresses. Since the IANA reserved IP address space is not used normally; therefore, a packet destined to such an address requires investigative analysis. If the destination IP address of an IP packet is in the IANA reserved IP address space, method  200  proceeds to step  225 ; otherwise, the method proceeds to step  235 .  
         [0035]     In step  225 , method  200  checks if the destination IP address of the IP packet in the IANA reserved IP address space is an allowed IANA IP address stored in the allowed reserved IANA IP address memory table. If the destination IP address of an IP packet is in the allowed IANA reserved IP address space, method  200  proceeds to step  235 ; otherwise, the method proceeds to step  230 . In step  230 , method  200  executes sub-method  400  “Add Possible Worm” shown in  FIG. 4  to increment by one the cumulative count of this source IP address entry as an IANA reserved space violation with the current timestamp. Then, the method proceeds to step  255 . Reserved IANA IP addresses are illustratively shown in TABLE 1 below. The most up-to-date IANA reserved IP address space can be found at http://www.iana.org/assignments/ipv4-address-space.  
               TABLE 1                       IANA reserved IP addresses (Valid on 03/18/2005,       IANA may change it later.)                   0.0.0.0-2.255.255.255       5.0.0.0-5.255.255.255       7.0.0.0-7.255.255.255       23.0.0.0-23.255.255.255       27.0.0.0-27.255.255.255       31.0.0.0-31.255.255.255       36.0.0.0-37.255.255.255       39.0.0.0-39.255.255.255       41.0.0.0-42.255.255.255       49.0.0.0-50.255.255.255       73.0.0.0-79.255.255.255        89.0.0.0-123.255.255.255       127.0.0.0-127.255.255.255       173.0.0.0-187.255.255.255       189.0.0.0-190.255.255.255       197.0.0.0-197.255.255.255       223.0.0.0-223.255.255.255       240.0.0.0-255.255.255.255                  
 
         [0036]     In step  235 , method  200  checks if the packet is an ICMP type 3 packet with code 0 (network unreachable), code 1 (host unreachable), code 2 (protocol unreachable) or code 3 (port unreachable). An ICMP type 3 packet format is shown in  FIG. 6 . If the packet is an ICMP type 3 with code 0, 1, 2 or 3 packet, the method proceeds to step  240 ; otherwise, proceeds back to step  215 . In step  240 , method  200  checks if the destination IP address of the packet is in the authorized scan system IP address memory table. If the destination IP address of the packet is in the authorized scan system IP address memory table, the method proceeds back to step  215 ; otherwise, the method proceeds to step  245 .  
         [0037]     In step  245 , method  200  extracts from the header of the original IP packet embedded in the ICMP type 3 packet to obtain the source IP address, the destination IP address, the protocol information, and the port information. Method  200  counts the original IP packet as an ICMP type 3 IP address violation. An ICMP type 3 with code 0, 1, 2 and 3 packet format is shown in  FIG. 6 . The method then proceeds to step  250 . Note that from this step onward, method  200  uses the content source IP address and the content destination IP address extracted from the header of the original IP packet which is part of the content of ICMP unreachable packets. The reason is that ICMP unreachable packets were the reply packets due to unreachable destination network, host, protocol, or port. A worm infected system may originate packets to multiple destinations while the reply ICMP unreachable packets will indicate that these unreachable packets originate from a single source IP address to a single destination. In order to solve this problem, original source IP address and destination IP address are extracted from the original IP packet, which is part of the content of an ICMP packet, in order to determine whether those original IP packets are sent to multiple destination IP addresses from a single source IP address. For example, the worm infected computer 9.200.200.5 sends worm packets to IP addresses 9.100.100.111 and 9.100.100.222. If both IP addresses do not have live systems, the end router 9.100.100.1 sends two host unreachable packets back to the worm infected computer. Both of these two host unreachable packets are replied by router 9.100.100.1 to the worm infected computer 9.200.200.5. Only the contents of these two ICMP packets are different. One contains original header to destination 9.100.100.111 while the other contains original header to destination 9.100.100.222.  
         [0038]     In step  250 , method  200  executes the sub-method  400  “Add Possible Worm” shown in  FIG. 4  to increment by one the cumulative count of all source IP addresses associated with IP packets that produce ICMP error code, e.g., unreachable destination IP address (e.g., network and/or host), unreachable protocol, and unreachable port. In step  255 , method  200  checks if one of the worm probe devices has a source IP address associated with IP packets that produce a cumulative count that exceeds the predefined global threshold within a predefined global time period. The predefined global threshold is a configurable parameter specified by the worm probe operator. In one embodiment, the default global threshold of the cumulative count is 10 times the number of worm probes and the default predefined global time period is 2 seconds. If any of the worm probe devices has a source IP address associated with IP packets that produce ICMP type 3 IP address violation or IANA reserved IP address violation cumulative count that exceeds the predefined global threshold within the predefined global time period, the method proceeds to step  260 ; otherwise, the method proceeds to step  290 .  
         [0039]     In step  260 , method  200  marks the source IP address in the Global Table with worm IP address x with a current timestamp UTCx and sends the Worm IP address x and its associated timestamp UTCx to other worm probes, and informs human operators using multiple means including, but are not limited to, emails and pagers etc. The method then proceeds to step  265 . In step  265 , method  200  checks if the worm probe is running in worm infected system identification only mode or in worm infected system identification and disabling mode. If the worm probe is in the worm infected system identification only mode, the method proceeds back to step  215 ; otherwise, the method proceeds to step  270  to disable worm infected system. If a worm probe is running in worm infected system identification only mode, the worm probe will only identify worm infected systems but will not disable them. If a worm probe is running in worm infected system identification and disabling mode, the worm probe will identify worm infected systems and then disable them. The Global Table is a table that keeps track of a list of possible source IP addresses and associated data, such as cumulative count and timestamp, which have been identified globally as possible worm infected systems.  
         [0040]     The data structure of the Global Table is shown in  FIG. 9 . Data Structure  900  comprises 5 entry points for this table. Entry point  901  is for IANA reserved IP address violation, entry  902  point is for ICMP network unreachable violation, entry  903  point is for ICMP host unreachable violation, entry  904  point is for ICMP protocol unreachable violation, or entry  905  point is for ICMP port unreachable violation. For each entry point, a set of similar underlying data structures are associated with it. For instance, entry point  903  has a set of 8 data structures comprising data structures  901  through  917 . Each data structure,  901  to  917 , comprises a source IP address entry, a cumulative count entry, and a timestamp entry. These data structures are sorted and ordered by the source IP address entry.  
         [0041]     In step  270 , method  200  checks if the worm probe has already instructed routers or switches to block this identified worm infected system. If it has not issued blocking instructions, the method proceeds to step  285 ; otherwise, the method proceeds to step  275 . In step  275 , method  200  checks if the blocking request exceeds a predefined time threshold to complete the blocking task. If the predefined time threshold to complete the blocking task is exceeded, the method proceeds to step  280 ; otherwise, the method proceeds back to step  215 . In step  280 , method  200  marks the source IP address in the Global Table with worm IP address x fails to block with a current timestamp UTCx, sends the worm IP address x and the failure to block timestamp UTCx to other worm probes, and informs human operators using multiple means including, but are not limited to, emails and pagers etc. Although the worm is not blocked, the system has detected the worm and will report to the operators who can investigate and unplug the worm infected system manually. Then, the method proceeds back to step  215 .  
         [0042]     In step  285 , method  200  uses a technique similar to the traceroute command to identify the router or switch that is still reachable and the closest to the identified source IP address computer system. The method then instructs the identified router or switch to block all traffic from the identified source IP address. Then, method  200  proceeds to step  287 . In step  287 , method  200  marks the source IP address in the Global Table with worm IP address x successfully blocked with a current timestamp UTCx, sends the worm IP address x and the success to block timestamp UTCx to other worm probes, and informs human operators using multiple means including, but are not limited to, emails and pagers etc. Then, the method proceeds back to step  215 .  
         [0043]     In step  290 , method  200  checks if one of the worm probes has a source IP address associated with IP packets that produce a cumulative count that exceeds the predefined local threshold within a predefined local time period. The predefined local threshold is a configurable parameter specified by the worm probe operator. In one embodiment, the default local threshold is  10  and the default local time period is 1 second. If any of the worm probes has a source IP address associated with IP packets that produce ICMP type 3 IP address violation or IANA reserved IP address violation cumulative count that exceeds the predefined local threshold within predefined local time period, the method proceeds to step  295 ; otherwise, the method proceeds back to step  215 .  
         [0044]     In step  295 , method  200  sends this possible worm IP address that exceeds the local threshold within the predefined local time period from the worm probe device that detects the threshold crossing to all other worm probes in the network. The method then proceeds back to step  215 .  
         [0045]      FIG. 3  illustrates a flowchart of sub-method “Possible worm IP address table periodical clearing” for identifying and disabling TCP/IP worm infected systems of the present invention. This is a very important sub-process because without this clearing sub-process to delete those outdated source IP address entries, method  200  will lead to false positive identification of worm infected systems because not all IANA reserved IP address-violations and ICMP unreachable violations are caused by TCP/IP worms. Only those IANA violation packets and ICMP unreachable packets which have the pattern of one source IP address with multiple destination IP addresses within a short time period are originated by TCP/IP worms or scan machines. After the worm probe main method, method  200 , starts to run, the “Local possible worm IP address table”, referred to as the Local Table hereafter, and the “Global possible worm IP address table”, referred to as the Global Table hereafter, contains IP addresses which are associated with IANA reserve IP address violations and ICMP unreachable violations. The Global Table is a table that keeps track of a list of possible source IP addresses and associated data, such as cumulative count and timestamp, which have been identified globally as possible worm infected systems. The Local Table is a table that keeps track of a list of possible source IP addresses and associated data, such as cumulative count and timestamp, which have been identified locally as possible worm infected systems. Method  300  is used to clear up those exceeded time period IP address entries from memory tables. Method  300  starts in step  305  and proceeds to step  310 .  
         [0046]     The data structure of the Local Table is shown in  FIG. 8 . Data Structure  800  comprises 5 entry points for this table. Entry point  801  is for IANA reserved IP address violation, entry  802  point is for ICMP network unreachable violation, entry  803  point is for ICMP host unreachable violation, entry  804  point is for ICMP protocol unreachable violation, or entry  805  point is for ICMP port unreachable violation. For each entry point, a set of similar underlying data structures are associated with it. For instance, entry point  803  has a set of 3 source IP address data structures  810 ,  820 , and  830 . Each of these source IP address data structures,  810 ,  820 , and  830 , comprises a source IP address entry and a cumulative count entry. In addition, each of the source IP address data structure has a set of one or more underlying destination IP address data structures associated with it. For instance, for the source IP address data structure  810  with source IP address A, it has a set of 3 underlying destination IP address data structures,  811 ,  812 , and  813 , associated with it. Each of the destination IP address data structures comprises a destination IP address entry and a timestamp entry. Similarly, the source IP address data structure  820  with source IP address B, it has a set of 8 underlying destination IP address data structures,  821  through  828 , associated with it and the source IP address data structure  830  with source IP address C, it has a set of 2 underlying destination IP address data structures,  831  and  832 , associated with it. The source IP address data structures are sorted and ordered by the source IP address and the underlying destination IP address data structures are sorted and ordered by the destination IP address.  
         [0047]     The data structure of the Global Table is shown in  FIG. 9 . Data Structure  900  comprises 5 entry points for this table. Entry point  901  is for IANA reserved IP address violation, entry  902  point is for ICMP network unreachable violation, entry  903  point is for ICMP host unreachable violation, entry  904  point is for ICMP protocol unreachable violation, or entry  905  point is for ICMP port unreachable violation. For each entry point, a set of similar underlying data structures are associated with it. For instance, entry point  903  has a set of 8 data structures comprising data structures  901  through  917 . Each data structure,  901  to  917 , comprises a source IP address entry, a cumulative count entry, and a timestamp entry. These data structures are sorted and ordered by the source IP address entry.  
         [0048]     In step  310 , method  300  accesses the computer system time which is synchronized to the Universal Time Clock using the Network Timing Protocol protocol. The Network Time Protocol is a protocol used to synchronize time between computers on the Internet. In step  315 , method  300  accesses the first destination IP address entry in Local Table. In step  320 , method  300  checks if the value of (current time—timestamp associated with the destination IP address in the Local Table) exceeds the predefined local time period of this destination IP address. If the value exceeds the predefined local time period, the method proceeds to  325 ; otherwise, the method proceeds to step  340 . In step  325 , method  300  deletes this destination IP address entry and frees the memory allocation to the memory pool. The source IP address cumulative count in the Local Table, which is associated with this destination IP address, is decremented by 1. In step  330 , method  300  checks if the source IP address cumulative count is 0 in the Local Table. If the source IP address cumulative count is 0, the method proceeds to step  335 ; otherwise, the method proceeds to step  340 .  
         [0049]     In step  335 , method  300  deletes this source IP address entry and frees the memory allocation to memory pool. This means that during the predefined local time period, this source IP address did not send IP packets to a lot of multiple destination IP addresses which are in the IANA reserved IP address space or which are unreachable. In step  340 , method  300  checks if this source IP address is the last destination IP address entry in the Local Table. If the source IP address is the last destination IP address entry in the Local Table, method  300  has finished processing “Local Table” clearing and proceeds to step  350  to process “Global Table” clearing; otherwise, method  300  proceeds to step  345 . In step  345 , method  300  accesses the next destination IP address entry in the Local Table and proceeds back to step  320 .  
         [0050]     In step  350 , method  300  accesses the first source IP address entry in the Global Table. In step  355 , method  300  checks if this source IP address in the Global Table is a worm that has been identified, has been successfully blocked or has failed to be blocked. If this source IP address in the Global Table is a worm that has been identified, has been successfully blocked or has failed to be blocked, method  300  proceeds to step  370 ; otherwise, method  300  proceeds to step  360 . In step  360 , method  300  checks if the value of (current time—timestamp associated with the source IP address in the Global Table) exceeds the predefined global time period of this source IP address. If the value exceeds the predefined global time period, the method proceeds to  365 ; otherwise, the method proceeds to step  370 . In step  365 , method  300  deletes this source IP address entry and frees the memory allocation to the memory pool.  
         [0051]     In step  370 , method  300  checks if it is the last source IP address entry in the Global Table. If it is, method  300  proceeds to step  380 ; otherwise, the method proceeds to step  375 . In step  375 , method  300  accesses the next source IP address entry in the Global Table and proceeds back to step  355 . In step  380 , method  300  waits until the end of the predefined local time period. At that time, method  300  proceeds back to step  310 .  
         [0052]      FIG. 4  illustrates a flowchart of sub-method “Add possible worm” for identifying and disabling TCP/IP worm infected systems of the present invention. Method  400  is executed and called by method  200  to add possible worm IP address to the Local Table and the Global Table. Method  400  starts in step  405  and proceeds to step  410 .  
         [0053]     In step  410 , method  400  selects the entry point in the Local Table based on IANA reserved IP address violation, ICMP network unreachable violation, ICMP host unreachable violation, ICMP protocol unreachable violation, or ICMP port unreachable violation. In step  415 , method  400  checks the source IP address whether it is already in the Local Table by searching the sorted IP address entries in the Local Table. If the source IP address is found, method  400  proceeds to step  425 ; otherwise, the method proceeds to  420 . In step  420 , method  400  allocates a memory structure from the system memory pool for the source IP address, fills in the source IP address and sets the source IP address cumulative count to 1. Method  400  also allocates a memory structure from the system memory pool for the destination IP address, fills in the destination IP address with the current timestamp. Note that for each source IP address data structure, there will be one or more destination IP address data structures that are associated with each source IP address data structure. Thus, in one embodiment, the source IP address has a count of the destination IP addresses, and the destination IP addresses have the current time timestamp. Method  400  then inserts these memory structures into the Local Table and keeps the source IP address sorted.  
         [0054]     In step  425 , method  400  checks if the destination IP address is already in the Local Table associated with a source IP address by searching the sorted IP address entries in the Local Table. If the destination IP address is found in the Local Table, method  400  proceeds to step  430 ; otherwise, the method proceeds to  440 . In step  430 , method  400  updates the destination IP address entry with the current timestamp. Then the method proceeds to step  435  to return to method  200 . In step  440 , method  400  increments by one the source IP address cumulative count. Method  400  also allocates a memory structure from the system memory pool for the destination IP address, fills in the destination IP address with the current timestamp. Then, method  400  inserts the destination IP address memory structure into the corresponding source IP address entry in the Local Table and keeps the destination IP addresses sorted.  
         [0055]     In step  445 , method  400  selects the entry point in the Global Table based on IANA reserved IP address violation, ICMP network unreachable violation, ICMP host unreachable violation, ICMP protocol unreachable violation, or ICMP port unreachable violation. In step  450 , method  400  checks if the source IP address is already in the Global Table by searching the sorted IP address entries in the Global Table. If the source IP address is found, method  400  proceeds to step  455 ; otherwise, the method proceeds to  465 . In step  455 , method  400  increments by one the source IP address cumulative count and updates the timestamp to this source IP address entry in the Global Table. Then the method proceeds to step  460  to return to method  200 .  
         [0056]     In step  465 , method  400  checks if the local source IP address cumulative count exceeds the predefined local threshold. If the local source IP address cumulative count exceeds the predefined local threshold, the method proceeds to  475 ; otherwise, the method proceeds to step  470  to return to method  200 . In step  475 , method  400  allocates a memory structure from the system memory pool for the source IP address, copies the source IP address and the source IP address cumulative count into the memory structure, sets the timestamp with the current time. Then, method  400  inserts this memory structure into the Global Table and keep the source IP address sorted. Then, the method proceeds to step  480  to return to method  200 .  
         [0057]      FIG. 5  illustrates a flowchart of sub-method “Receive Global Change” for identifying and disabling TCP/IP worm infected systems of the present invention. Method  500  is the sub-method that receives and updates changes sent from other worm probes. Method  500  starts in step  505  and proceeds to step  510 .  
         [0058]     In step  510 , method  500  listens and waits until it receives global change information from other worm probes. In step  515 , method  500  checks if the received global change information is a “Global setting change” or a “Global possible worm IP address change” sent by other worm probes. If it is the “Global setting change”, the method proceeds to step  520 ; otherwise, the method proceeds to step  525 .  
         [0059]     In step  520 , method  500  copies those “Global settings change” information into the worm probe settings memory tables. Then, the method proceeds back to step  510 . In step  525 , method  500  selects the entry point in the Global Table based on IANA reserved IP address violation, ICMP network unreachable violation, ICMP host unreachable violation, ICMP protocol unreachable violation, or ICMP port unreachable violation.  
         [0060]     In step  530 , method  500  checks if the received IP address is already in the Global Table. If the received IP address is already in the Global Table, the method proceeds to step  550 ; otherwise, the method proceeds to step  535 . In step  535 , method  500  allocates a memory structure from the system memory pool for the source IP address, copies the source IP address and the source IP address cumulative count into the memory structure, and sets the timestamp to the current time. Then, method  500  inserts this memory structure into the Global Table and keeps the source IP address sorted.  
         [0061]     In step  540 , method  500  selects the entry point in the Local Table based on IANA reserved IP address violation, ICMP network unreachable violation, ICMP host unreachable violation, ICMP protocol unreachable violation, or ICMP port unreachable violation. In step  545 , method  500  checks if the received IP address is also in the Local Table. If the received IP address is also in the Local Table, the method proceeds to step  555 ; otherwise, the method proceeds back to step  510 .  
         [0062]     In step  550 , method  500  adds the received source IP address cumulative count into the existing source IP address entry, and updates the timestamp in the Global Table. In step  555 , method  500  adds the source IP address cumulative count of the Local Table into this new source IP address entry in the Global Table. In step  560 , method  500  sends the source IP address cumulative count in the Local Table to other worm probes. In step  565 , method  500  checks if the source IP address cumulative count exceeds the predefined global threshold. If the predefined global threshold is not exceeded, the method  500  proceeds back to step  510 . If it is exceeded, method  500  proceeds to step  570 . Step  570  identifies and blocks worm source IP address by using method  200  steps  260 ,  265 ,  270 ,  275 ,  280 ,  285  and  287 . Then, method  500  proceeds back to step  510 .  
         [0063]     The architecture of the present invention may comprise the following components: 
        The worm probe devices can be any general purpose computer systems with the equivalent processing power of an Intel based Pentium IV 3.0 GHz CPU with at least 1 GB RAM and a gigabit Ethernet NIC running LINUX OS with the Sniffer application capability. A Sniffer application is a program and/or device that monitors all data packets traveling over a network segment which the computer NIC card is plugged in. All worm probe devices must be configured to run NTP (Network Time Protocol) peer services to synchronize the time to UTC (Universal Time Clock). The worm probe application can be in the form of, but is not limited to, a C language executable application.     The worm probe devices are deployed in the internal networks of an entity, e.g., a company, such as a LAN or main traffic aggregation hubs or exchange points with heavy IP traffic load in the network, such as border router, firewall, proxy, VPN concentrator, IDS and IPS segments. Every segregated network can have at least one probe device deployed at IP node with heavy traffic. A big global network will have about a dozen of worm probes deployed within the network.     Routers deployed within the company internal networks should be compliant to Internet Engineering Task Force (IETF) Request For Comments (RFC)  792  or routing based on IANA reserved IP addresses or both.     The worm probes use the TACACS+ method to communicate with routers and switches to block infected computer systems. TACACS+ is a security application that provides centralized validation of users attempting to gain access to a router or network access server.        
 
         [0068]      FIG. 7  depicts a high level components diagram of a general purpose computer suitable for use in performing the functions described herein. As depicted in  FIG. 7 , the system  700  comprises a processor element  702  (e.g., a CPU), a memory  704 , e.g., random access memory (RAM) and/or read only memory (ROM), an identifying and disabling TCP/IP worm module  705 , and various input/output devices  706  (e.g., storage devices, including but not limited to, a tape drive, a floppy drive, a hard disk drive or a compact disk drive, a receiver, a transmitter, a speaker, a display, a speech synthesizer, an output port, and a user input device (such as a keyboard, a keypad, a mouse, and the like)).  
         [0069]     It should be noted that the present invention can be implemented in software and/or in a combination of software and hardware, e.g., using application specific integrated circuits (ASIC), a general purpose computer or any other hardware equivalents. In one embodiment, the present identifying and disabling TCP/IP worm module or process  705  can be loaded into memory  704  and executed by processor  702  to implement the functions as discussed above. As such, the present identifying and disabling TCP/IP worm process  705  (including associated data structures) of the present invention can be stored on a computer readable medium or carrier, e.g., RAM memory, magnetic or optical drive or diskette and the like.  
         [0070]     While various embodiments have been described above, it should be understood that they have been presented by way of example only, and not limitation. Thus, the breadth and scope of a preferred embodiment should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.