Patent Publication Number: US-10785266-B2

Title: Methods and systems for protecting a secured network

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation of co-pending U.S. patent application Ser. No. 16/111,524, filed Nov. 25, 2019, entitled “METHOD AND SYSTEMS FOR PROTECTING A SECURED NETWORK”, which is a continuation of U.S. patent application Ser. No. 15/413,834, filed Jan. 24, 2017 (now U.S. Pat. No. 10,091,246), entitled “METHODS AND SYSTEMS FOR PROTECTING A SECURED NETWORK,” which is a continuation of U.S. patent application Ser. No. 14/698,560 (now U.S. Pat. No. 9,560,077), filed Apr. 28, 2015, entitled “METHODS AND SYSTEMS FOR PROTECTING A SECURED NETWORK,” which is a continuation of U.S. patent application Ser. No. 13/657,010 (now U.S. Pat. No. 9,137,205), filed Oct. 22, 2012, entitled “METHODS AND SYSTEMS FOR PROTECTING A SECURED NETWORK.” The disclosures of each of these applications are incorporated by reference herein in their entirety and made part hereof. 
    
    
     BACKGROUND 
     The TCP/IP network protocols (e.g., the Transmission Control Protocol (TCP) and the Internet Protocol (IP)) were designed to build large, resilient, reliable, and robust networks. Such protocols, however, were not originally designed with security in mind. Subsequent developments have extended such protocols to provide for secure communication between peers (e.g., Internet Protocol Security (IPsec)), but the networks themselves remain vulnerable to attack (e.g., Distributed Denial of Service (DDoS) attacks). 
     Most existing approaches to protecting such networks are reactive rather than proactive. While reactive approaches may identify the source of an attack and assist in subsequent mitigation efforts, in most instances, the attack will have already been successfully launched. 
     Proactive solutions, however, have often been deemed untenable due to an inability to scale to larger networks. A significant challenge associated with building a scalable proactive solution is the need to filter substantially all network traffic at a high resolution. In a large network, where traffic volumes may be enormous, the time required to provide high resolution filtering has traditionally been thought to render a proactive solution infeasible. 
     SUMMARY 
     The following presents a simplified summary in order to provide a basic understanding of some aspects of the disclosure. It is neither intended to identify key or critical elements of the disclosure nor to delineate the scope of the disclosure. The following summary merely presents some concepts in a simplified form as a prelude to the description below. 
     Aspects of this disclosure relate to protecting a secured network. In some embodiments, one or more packet security gateways are associated with a security policy management server. At each of the packet security gateways, a dynamic security policy may be received from the security policy management server, packets associated with a network protected by the packet security gateway may be received, and at least one of multiple packet transformation functions specified by the dynamic security policy may be performed on the packets. Performing the at least one of multiple packet transformation functions specified by the dynamic security policy on the packets may include performing at least one packet transformation function other than forwarding or dropping the packets. 
     In some embodiments, two or more of the packet security gateways may be configured in series such that packets forwarded from a first of the packet security gateways are received by a second of the packet security gateways. In some embodiments, the dynamic security policy may include two rules requiring sequential execution. A first of the packet security gateways may perform a packet transformation function specified by one of the rules on the packets and a second of the packet security gateways may subsequently perform a packet transformation function specified by the other of the rules on packets received from the first packet security gateway. 
     In some embodiments, the dynamic security policy may include a rule specifying a set of network addresses for which associated packets should be dropped and a rule specifying that all packets associated with network addresses outside the set should be forwarded. Additionally or alternatively, the dynamic security policy may include a rule specifying a set of network addresses for which associated packets should be forwarded and a rule specifying that all packets associated with network addresses outside the set should be dropped. In some embodiments, the security policy management server may receive information associated with one or more Voice over Internet Protocol (VoIP) sessions and the set of network addresses for which associated packets should be forwarded may be created or altered utilizing the information associated with the one or more VoIP sessions. 
     In some embodiments, the packet security gateways may receive three or more dynamic security policies from the security policy management server. A first of the dynamic security policies may specify a first set of network addresses for which packets should be forwarded. A second of the dynamic security policies may be received after the first and may specify a second set of network addresses, which includes more network addresses than the first set, for which packets should be forwarded. A third of the dynamic security policies may be received after the second and may specify a third set of network addresses, which includes more network addresses than the second set, for which packets should be forwarded. 
     In some embodiments, the dynamic security policy may include two rules that each specify a set of network addresses. The dynamic security policy may specify that packets associated with the first set of network addresses should be placed in a first forwarding queue and packets associated with the second set of network addresses should be placed in a second forwarding queue. The first forwarding queue may have a different queueing policy, for example, a higher forwarding rate, than the second forwarding queue. 
     In some embodiments, the dynamic security policy may include a rule specifying a set of network addresses and an additional parameter. The packet transformation function specified by the dynamic security policy may include routing packets that fall within the specified set and match the additional parameter to a network address different from a destination network address specified by the packets. In some embodiments, the additional parameter may be a Session Initiation Protocol (SIP) Uniform Resource Identifier (URI). The network address different from the destination network address may correspond to a device configured to copy information contained within the packets and forward the packets to the destination network address specified by the packets. 
     In some embodiments, the packet transformation function may forward the packets into the network protected by the packet security gateway. In some embodiments, the packet transformation function may forward the packets out of the network protected by the packet security gateway. In some embodiments, the packet transformation function may forward the one or more packets to an IPsec stack having an IPsec security association corresponding to the packets. In some embodiments, the packet transformation function may drop the packets. 
     In some embodiments, the dynamic security policy may include multiple rules. One of the rules may specify the packet transformation function. In some embodiments, one of the rules may specify a five-tuple of values selected from packet header information. The five-tuple may specify one or more protocol types, one or more IP source addresses, one or more source ports, one or more IP destination addresses, and one or more destination ports. In some embodiments, one of the rules may specify a Differentiated Service Code Point (DSCP) that maps to a DSCP field in an IP header of one of the packets. 
     In some embodiments, one of the packet security gateways may operate in a network layer transparent manner. For example, the packet security gateway may send and receive traffic at a link layer using an interface that is not addressed at the network layer and simultaneously perform the packet transformation function at the network layer. Additionally or alternatively, the packet security gateway may include a management interface having a network layer address. Access to the management interface may be secured at the application level. 
     In some embodiments, the dynamic security policy may include a rule generated based, at least in part, on a list of known network addresses associated with malicious network traffic. In some embodiments, the list of known network addresses associated with malicious network traffic may be received from a subscription service that aggregates information associated with malicious network traffic. 
     In some embodiments, the packets associated with the network protected by the packet security gateway may originate within the network protected by the packet security gateway and may be destined for a network distinct from the network protected by the packet security gateway. Additionally or alternatively, the packets associated with the network protected by the packet security gateway may originate within a network distinct from the network protected by the packet security gateway and may be destined for a host within the network protected by the packet security gateway. 
     In some embodiments, one of the packet security gateways may be located at each boundary between a protected network associated with the security policy management server and an unprotected network. 
     Other details and features will be described in the sections that follow. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present disclosure is pointed out with particularity in the appended claims. Features of the disclosure will become more apparent upon a review of this disclosure in its entirety, including the drawing figures provided herewith. 
       Some features herein are illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings, in which like reference numerals refer to similar elements. 
         FIG. 1  illustrates an exemplary network environment in which one or more aspects of the disclosure may be implemented. 
         FIG. 2  illustrates an exemplary packet security gateway. 
         FIG. 3  illustrates an exemplary dynamic security policy. 
         FIG. 4  illustrates an exemplary configuration of multiple packet security gateways in series. 
         FIG. 5  illustrates an exemplary security policy management server. 
         FIG. 6  illustrates an exemplary network environment for implementing a monitoring service. 
         FIG. 7  illustrates an exemplary network environment that includes a secured network having multiple boundaries with unsecured networks. 
         FIG. 8  illustrates an exemplary network environment that includes multiple distinct secured networks. 
         FIG. 9  illustrates an exemplary secure LAN environment. 
         FIG. 10  illustrates an exemplary method for protecting a secured network. 
     
    
    
     DETAILED DESCRIPTION 
     In the following description of various illustrative embodiments, reference is made to the accompanying drawings, which form a part hereof, and in which is shown, by way of illustration, various embodiments in which aspects of the disclosure may be practiced. It is to be understood that other embodiments may be utilized, and structural and functional modifications may be made, without departing from the scope of the present disclosure. 
     Various connections between elements are discussed in the following description. These connections are general and, unless specified otherwise, may be direct or indirect, wired or wireless. In this respect, the specification is not intended to be limiting. 
       FIG. 1  illustrates an exemplary network environment in which one or more aspects of the disclosure may be implemented. Referring to  FIG. 1 , network environment  100  may include networks A-E  102 ,  104 ,  106 ,  108 , and  110 . One or more networks within network environment  100  may be a Local Area Network (LAN) or a Wide Area Network (WAN). Such a LAN or WAN may be associated, for example, with an organization (e.g., a company, university, enterprise, or government agency). For example, networks A-D  102 ,  104 ,  106 , and  108  may be LANs, any combination of which may be associated with one or more organizations. One or more networks within network environment  100  may interface with one or more other networks within network environment  100 . For example, network environment  100  may include a WAN that interfaces one or more LANs within network environment  100  or network environment  100  may include one or more Internet Service Providers (ISPs) that interface one or more LANs or WANs within network environment  100  via the Internet. For example, network E  110  may comprise the Internet and may interface networks A-D  102 ,  104 ,  106 , and  108 . 
     As used herein, a packet security gateway includes any computing device configured to receive packets and perform a packet transformation function on the packets. Optionally, a packet security gateway may further be configured to perform one or more additional functions as described herein. As used herein, a security policy management server includes any computing device configured to communicate a dynamic security policy to a packet security gateway. Optionally, a security policy management server may further be configured to perform one or more additional functions as described herein. As used herein, a dynamic security policy includes any rule, message, instruction, file, data structure, or the like that specifies criteria corresponding to one or more packets and identifies a packet transformation function to be performed on packets corresponding to the specified criteria. Optionally, a dynamic security policy may further specify one or more additional parameters as described herein. 
     Network environment  100  may include one or more packet security gateways and one or more security policy management servers. For example, network environment  100  may include packet security gateways  112 ,  114 ,  116 , and  118 , and security policy management server  120 . One or more security policy management servers may be associated with a protected network. For example, networks A-D  102 ,  104 ,  106 , and  108  may each be distinct LANs associated with a common organization and may each form part of a protected network associated with security policy management server  120 . Many network protocols route packets dynamically, and thus the path a given packet may take cannot be readily predicted. Accordingly it may be advantageous to locate a packet security gateway at each boundary between a protected network and an unprotected network. For example, packet security gateway  112  may be located at the boundary between network A  102  and network E  110 . Similarly, packet security gateway  114  may be located at the boundary between network B  104  and network E  110 ; packet security gateway  116  may be located at the boundary between network C  106  and network E  110 ; and packet security gateway  118  may be located at the boundary between network D  108  and network E  110 . As will be described in greater detail below, each of one or more packet security gateways associated with a security policy management server may be configured to receive a dynamic security policy from the security policy management server, receive packets associated with a network protected by the packet security gateway, and perform a packet transformation function specified by the dynamic security policy on the packets. For example, each of packet security gateways  112 ,  114 ,  116 , and  118  may be configured to receive a dynamic security policy from security policy management server  120 . Each of packet security gateways  112 ,  114 ,  116 , and  118  may also be configured to receive packets respectively associated with networks A-D  102 ,  104 ,  106 , and  108 . Each of packet security gateways  112 ,  114 ,  116 , and  118  may further be configured to perform a packet transformation function specified by the dynamic security policy received from security policy management server  120  on the packets respectively associated with networks A-D  102 ,  104 ,  106 , and  108 . 
       FIG. 2  illustrates an exemplary packet security gateway according to one or more aspects of the disclosure. Referring to  FIG. 2 , as indicated above, packet security gateway  112  may be located at network boundary  200  between network A  102  and network E  110 . Packet security gateway  112  may include processor  202 , memory  204 , network interfaces  206  and  208 , packet filter  214 , and management interface  222 . Processor  202 , memory  204 , network interfaces  206  and  208 , packet filter  214 , and management interface  222  may be interconnected via data bus  210 . Network interface  206  may connect packet security gateway  112  to network E  110 . Similarly, network interface  208  may connect packet security gateway  112  to network A  102 . Memory  204  may include one or more program modules that when executed by processor  202 , configure packet security gateway  112  to perform various functions as described herein. 
     Packet security gateway  112  may be configured to receive a dynamic security policy from security policy management server  120 . For example, packet security gateway  112  may receive dynamic security policy  212  from security policy management server  120  via management interface  222  (i.e., out-of-band signaling) or network interface  206  (i.e., in-band signaling). Packet security gateway  112  may include one or more packet filters or packet discriminators, or logic for implementing one or more packet filters or packet discriminators. For example, packet security gateway  112  may include packet filter  214 , which may be configured to examine information associated with packets received by packet security gateway  112  and forward the packets to one or more packet transformation functions based on the examined information. For example, packet filter  214  may examine information associated with packets received by packet security gateway  112  (e.g., packets received from network E  110  via management interface  222  or network interface  206 ) and forward the packets to one or more of packet transformation functions 1-N  216 ,  218 , and  220  based on the examined information. 
     As will be described in greater detail below, dynamic security policy  212  may include one or more rules and the configuration of packet filter  214  may be based on one or more of the rules included in dynamic security policy  212 . For example, dynamic security policy  212  may include one or more rules specifying that packets having specified information should be forwarded to packet transformation function  216 , while all other packets should be forwarded to packet transformation function  218 . Packet transformation functions 1-N  216 ,  218 , and  220  may be configured to perform one or more functions on packets they receive from packet filter  214 . For example, packet transformation functions 1-N  216 ,  218 , and  220  may be configured to forward packets received from packet filter  214  into network A  102 , forward packets received from packet filter  214  to an IPsec stack having an IPsec security association corresponding to the packets, or drop packets received from packet filter  214 . In some embodiments, one or more of packet transformation functions 1-N  216 ,  218 , and  220  may be configured to drop packets by sending the packets to a local “infinite sink” (e.g., the /dev/null device file in a UNIX/LINUX system). 
     In some embodiments, packet security gateway  112  may be configured in a network layer transparent manner. For example, packet security gateway  112  may be configured to utilize one or more of network interfaces  206  and  208  to send and receive traffic at the link layer. One or more of network interfaces  206  and  208 , however, may not be addressed at the network layer. Because packet filter  214  and packet transformation functions 1-N  216 ,  218 , and  220  operate at the network layer, PSG  112  may still perform packet transformation functions at the network layer. By operating in a network layer transparent manner, packet security gateway  112  may insulate itself from network attacks (e.g., DDoS attacks) launched at the network layer because attack packets cannot be routed to the network interfaces  206  and  208 . In some embodiments, packet security gateway  112  may include management interface  222 . Management interface  222  may be addressed at the network level in order to provide packet security gateway  112  with network level addressability. Access to management interface  222  may be secured, for example, at the application level by using a service such as SSH, or secured at the transport level using, e.g., TLS, or secured at the network level by attaching it to a network with a separate address space and routing policy from network A  102  and network E  110 , or secured at the link level, e.g., using the IEEE 802.1X framework, etc. 
     The flows illustrated by  FIG. 2  are merely exemplary and show packets that originate within a network distinct from network A  102  and are destined for a host within network A  102  in order to simplify the illustration. Packet security gateway  112  may be configured to receive and filter packets that originate within a network other than network A  102  (e.g., networks B-E  104 ,  106 ,  108 , or  110 ) and are destined for a host within network A  102 , as well as packets that originate within network A  102  destined for a network distinct from network A  102  (e.g., network B-D  104 ,  106 ,  108 , or  110 ). That is, packet security gateway  112  may be configured to filter and perform one or more packet transformation functions on packets flowing in either direction and may thus be utilized, for example, to both protect network A  102  from malicious network traffic and to prevent malicious network traffic from leaving network A  102 . 
       FIG. 3  illustrates an exemplary dynamic security policy in accordance with one or more embodiments. Referring to  FIG. 3 , dynamic security policy  300  may include rules 1-5  302 ,  304 ,  306 ,  308 , and  310 . Each rule may specify criteria and one or more packet transformation functions that should be performed for packets associated with the specified criteria. The specified criteria may take the form of a five-tuple of values selected from packet header information, specifying a protocol type of the data section of the IP packet (e.g., TCP, UDP, ICMP, or any other protocol), one or more source IP addresses, one or more source port values, one or more destination IP addresses, and one or more destination ports. For example, rule 1  302  may specify that IP packets containing TCP packets, originating from a source IP address that begins with 140, having any source port, destined for an IP address that begins with 130, and destined for port 20 should have an accept packet transformation function (e.g., the identity function) performed on them. Similarly, rule 2  304  may specify that IP packets containing TCP packets, originating from a source IP address that begins with 140, having any source port, destined for any IP address, and destined for port 80 should have an accept packet transformation function performed on them; rule 3  306  may specify that IP packets containing TCP packets, originating from a source IP address that begins with 150, having any source port, destined for any IP address that begins with 120, and destined for port 90 should have an accept packet transformation function performed on them; rule 4  308  may specify that IP packets containing UDP packets, originating from a source IP address that begins with 150, having any source port, destined for any IP address, and destined for port 3030 should have an accept packet transformation function performed on them; and rule 5  310  may specify that IP packets containing any data, originating from any source IP address, having any source port, destined for any IP address, and destined for any port should have a deny packet transformation function performed on them. One or more rules included in dynamic security policy  300  may be specified in IP version 4 or IP version 6. 
     As will be described in greater detail below, dynamic security policy  300  may include one or more rules that specify a packet transformation function other than forwarding (accepting or allowing) or dropping (denying) a packet. For example, rule 3  306  may specify that IP packets containing TCP packets, originating from a source IP address that begins with 150, having any source port, destined for any IP address that begins with 120, and destined for port 90 should not only have an accept packet transformation function performed on them, but should also be routed to a monitoring device. 
     One or more rules within dynamic security policy  300  may be required to execute in a specific order. For example, it may be required that rule 5  310  be executed last. Because rule 5  310  specifies that any packet should have a deny packet transformation function performed on it, if it were executed before a rule specifying an accept packet transformation function (e.g., one or more of rules 1-4  302 ,  304 ,  306 , or  308 ), no packets matching the criteria specified by the rule specifying the accept packet transformation function would pass through a packet security gateway implementing dynamic security policy  300 . Similarly, two or more rules within dynamic security policy  300  may specify overlapping criteria and different packet transformation functions. In such cases, the order-of-application of the rules may determine which rule is applied to a packet that would match the two or more rules. Such rules may be merged together or otherwise transformed into a different set of rules without overlapping criteria, which may produce the same result as the original set of rules, when applied to any packet. 
     A dynamic security policy may utilize the combination of one or more rules to create policies for governing packets within a network environment or effectuating one or more services within a network environment. For example, a dynamic security policy may include one or more rules, the combination of which may effectuate a blocklist service within a network environment. A dynamic security policy that effectuates a blocklist service within a network environment may include one or more rules specifying criteria (e.g., a set of network addresses) for which associated packets should be blocked, dropped, or denied, and at least one rule specifying that all packets outside the specified block sets should be forwarded, accepted, or allowed. Such a dynamic security policy may be constructed by including one or more rules specifying criteria (e.g., a set of network addresses) for which associated packets should be dropped, and a wildcard rule, designated to be executed last, and specifying that all packets should be allowed. One or more dynamic security policies that effectuate a blocklist service may be utilized to implement one or more Virtual Private Networks (VPNs). 
     A dynamic security policy may also include one or more rules, the combination of which may effectuate an allowlist service within a network environment. A dynamic security policy that effectuates an allowlist service within a network environment may include one or more rules specifying criteria (e.g., a set of network addresses) for which associated packets should be forwarded, allowed, or accepted, and at least one rule specifying that all packets outside the specified allow sets should be blocked, denied, or dropped. Such a dynamic security policy may be constructed by including one or more rules specifying criteria (e.g., a set of network addresses) for which associated packets should be forwarded, and a wildcard rule, designated to be executed last, and specifying that all packets should be blocked. For example, dynamic security policy  300  includes rules 1-4  302 ,  304 ,  306 , and  308 , each of which specifies a set of network addresses for which packets should be allowed, and rule 5  310  which specifies that all packets should be dropped. Thus, if rules 1-5  302 ,  304 ,  306 ,  308 , and  310  are executed in order, dynamic security policy  300  will effectuate an allowlist service. 
     A dynamic security policy may also include one or more rules, the combination of which may effectuate a VoIP firewall service within a network environment. As will be discussed in greater detail below, a security policy management server may receive information associated with VoIP sessions. For example, a security policy management server may receive information associated with VoIP sessions from one or more softswitches (e.g., H.323 softswitches, SIP IP Multimedia Subsystem (IMS) softswitches) or session border controllers when a VoIP session is initialized or set up. In order to allow packets associated with such a VoIP session within a network protected by one or more packet security gateways associated with the security policy management server, the security policy management server may utilize the received information associated with the VoIP sessions to construct one or more rules for allowing the packets associated with the VoIP session. When the VoIP session is terminated or torn down, the softswitch or session border controller may notify the security policy management server, which may create or alter one or more rules to reflect the termination of the VoIP session (e.g., to deny future packets which may match criteria previously associated with the VoIP session). 
     A dynamic security policy may also include one or more rules or rule sets, the combination of which may effectuate a phased restoration service within a network environment. Such a phased restoration service may be used in the event of a network attack (e.g., a DDoS attack). When an attack occurs a network may be overwhelmed with network traffic and be unable to route all or any of the traffic. In the event of such an attack, it may be beneficial to utilize a dynamic security policy which effectuates a phased restoration service. Such a dynamic security policy may include one or more rules or rule sets configured for execution in time-shifted phases. Each of the rules or rule sets may specify progressively larger sets of network addresses. For example, a dynamic security policy may include three rules or rule sets which may be configured for execution in time-shifted phases. A first of the rules or rule sets may specify a relatively small set of network addresses for which packets should be forwarded (e.g., network addresses corresponding to mission critical network devices). A second of the rules or rule sets may specify a relatively larger set of network addresses for which packets should be forwarded (e.g., network addresses corresponding to trusted network devices). A third of the rules or rule sets may specify an even larger set of network addresses for which packets should be forwarded (e.g., network addresses corresponding to all network devices that would be allowed under ordinary circumstances). The dynamic security policy may specify that the rules or rule sets should be implemented in time-shifted phases. That is, the dynamic security policy may specify that the first rule or rule set should be executed first, and that the second rule or rule set should be executed at a time after the time at which the first rule or rule set is executed, and the third rule or rule set should be executed at a time after the time at which the second rule or rule set is executed. Such a dynamic security policy may assist a network in recovering from an attack, by allowing the network to isolate itself from the attack or recover in a controlled manner. 
     A dynamic security policy may also include one or more rules, the combination of which may effectuate an enqueueing service within a network environment. A dynamic security policy that effectuates an enqueueing service may include one or more rules that specify sets of network addresses and packet transformation functions that queue packets in one or more queues corresponding to the sets. These queues may then be serviced at varying rates. For example, a dynamic security policy may include two rules, each of which specify a set of network addresses. A first of the rules may specify that packets corresponding to its specified set should be queued in a first forwarding queue. A second of the rules may specify that packets corresponding to its specified set should be queued in a second forwarding queue. The first forwarding queue may be serviced at a higher forwarding rate than the second forwarding queue. Such an enqueueing service may be utilized during or following a network attack, or generally to provide prioritized service to critical network devices (e.g., when network resources are strained). In some embodiments, one or more rules contained within a dynamic security policy may include an arbitrary selector which may correspond to one or more parameters or fields associated with a packet. For example, a dynamic security policy rule may include a Differentiated Service Code Point (DSCP) selector that corresponds to a DSCP field in an IP header. Thus, two packets having different values within the specified DSCP field may correspond to two distinct rules within a dynamic security policy and have different packet transformation functions performed on them. For example, two otherwise identical packets having different values within the specified DSCP field may be queued in two different forwarding queues that have different forwarding rates, and may thus receive differentiated service. 
     A dynamic security policy may also include one or more rules, the combination of which may effectuate a multi-dimensional routing service or a multi-dimensional switching service within a network environment. For example, in some embodiments, a dynamic security policy may include one or more rules that specify a set of network addresses and an additional parameter. Such rules may further specify a packet transformation function configured to route packets within the specified set of network addresses that match the additional parameter to a network address distinct from the packets&#39; respective destination network addresses. For example, the packet transformation function may be configured to encapsulate such packets (e.g., as described by Internet Engineering Task Force (IETF) Request For Comment (RFC) 2003) with an IP header specifying a network address different from their respective destination addresses. The packets may then be routed to the network address specified by the encapsulating IP header, which may correspond to a network device configured to utilize such packets or data contained within them, strip the IP header from the packets, and forward the packets to their respective destination addresses. In some embodiments, the packet transformation function may be configured to alter or modify the destination address of the packets, which may then be routed to the altered or modified destination address. Additionally or alternatively, the packet transformation function may be configured to assign such packets to a particular Layer-2 VLAN (e.g., as described by IEEE 802.1Q). The packets may then be switched to another device on the same VLAN, which may or may not be on the IP-layer path that the packet would have taken if it were routed according to the packet&#39;s destination IP address instead of being switched through the VLAN. 
     As will be described in greater detail below, in some embodiments a dynamic security policy may include one or more rules, the combination of which may effectuate an implementation of a multi-dimensional routing service for performing a monitoring service within a network environment. For example, a dynamic security policy may include one or more rules that specify a set of network addresses (e.g., a set of network addresses from which a call that is to be monitored is expected to originate within) and an additional parameter (e.g., a SIP URI corresponding to a caller to be monitored). As indicated above, such rules may further specify a packet transformation function configured to route or switch packets within the specified set of network addresses that match the additional parameter (e.g., the SIP URI) to a network address corresponding to a monitoring device. The network address corresponding to the monitoring device may be different from the packets&#39; destination network address (e.g., an address corresponding to the called party or a softswitch associated with the called party). For example, the packet transformation function may be configured to encapsulate the packets with an IP header specifying the network address corresponding to the monitoring device. The packets may then be routed (or rerouted) to the monitoring device, which may be configured to copy the packets or data contained within them (e.g., for subsequent review by a law enforcement or national security authority), strip the IP header from them, and then forward the packets to their destination address (e.g., the address corresponding to the called party or softswitch associated with the called party). 
     As indicated above, a significant challenge associated with building a scalable proactive solution for protecting a secured network, is the need to filter substantially all network traffic at a high resolution. Filtering traffic at a high resolution often requires the use of many rules. In a large network, where traffic volumes may be enormous, the time required to provide high resolution filtering (e.g., the time required to apply a large number of rules to a large volume of traffic) has traditionally been thought to render proactive network protection solutions infeasible. This concern may be particularly acute in network environments that utilize low-latency applications (e.g., VoIP). 
     Recent advances in packet filtering technology have reduced the time required to apply large rule sets to network traffic. For example, U.S. Patent Application Publication Nos. 2006/0195896 and 2006/0248580 to Fulp et al., and U.S. Patent Application Publication No. 2011/0055916 to Ahn, describe advanced packet filtering technologies, and are each incorporated by reference herein in their entireties. 
     One approach to providing high resolution filtering, while reducing the number of rules applied to network traffic, may be utilized when a dynamic security policy is combinatorially complete. For example, a dynamic security policy may be configured to allow bi-directional communication between a set of N internal hosts {I 1 , I 2 , . . . , I N } within a protected network and a set of M external hosts {E 1 , E 2 , . . . , E M } outside the protected network. To enable communications between the internal hosts and the external hosts, the dynamic security policy may be constructed to include a set of rules containing each possible combination of internal hosts and external hosts (e.g., {{I 1 , E 1 }, {I 1 , E 2 }, . . . {I 1 , E M }, {I 2 , E 1 }, {I 2 , E 2 }, . . . {I 2 , E M }, . . . , {I N , E 1 }, {I N , E 2 }, . . . {I N , E M }}), each of the rules being associated with an allow packet transformation function. Such a dynamic security policy would have N*M rules for allowing communication between the internal hosts and the external hosts that originate from one of the internal hosts and are destined for one of the external hosts, and an additional N*M rules for allowing communications between the internal hosts and the external hosts that originate from one of the external hosts and are destined for one of the internal hosts. An equivalent result may be achieved, however, by constructing two smaller dynamic security policies: a first dynamic security policy that includes rules specifying the N internal hosts (e.g., {{I 1 }, {I 2 }, . . . , {I N }}), each rule being associated with an accept packet transformation function; and a second dynamic security policy that includes rules specifying the M external hosts (e.g., {{E 1 }, {E 2 }, . . . , {E M }}), each rule being associated with an accept packet transformation function. Such a construct of dynamic security policies may be implemented using a system of packet security gateways configured in series. 
       FIG. 4  illustrates an exemplary configuration of multiple packet security gateways connected in series. Referring to  FIG. 4 , packet security gateway  112  may include one or more packet security gateways configured in series. For example, packet security gateway  112  may include packet security gateways 1-N  400 ,  402 , and  404 . Packet security gateways 1-N  400 ,  402 , and  404  may be configured so that packets forwarded by packet security gateway 1  400  are received by packet security gateway 2  402 , and packets forwarded by packet security gateway 2  402  are received by the next packet security gateway in the series, all the way through packet security gateway N  404 . Each of packet security gateways 1-N  400 ,  402 , and  404  may include a packet filter, similar to packet filter  214  described above with respect to  FIG. 2 , and one or more packet transformation functions, similar to packet transformation functions 1-N  216 ,  218 , and  220  described above with respect to  FIG. 2 . Packet security gateways 1-N  400 ,  402 , and  404  may be utilized to implement a construct of dynamic security policies similar to that described above. 
     For example, packet security gateway 1  400  may be configured to implement P 1 , which may include rules specifying M external hosts (e.g., {{E 1 }, {E 2 }, . . . , {E M }}), each rule being associated with an accept packet transformation function. Packet security gateway 2  402  may be configured to implement P 2 , which may include rules specifying N internal hosts (e.g., {{I 1 }, {I 2 }, . . . , {I N }}), each rule being associated with an accept packet transformation function. A packet received by packet security gateway  112  may be initially received via packet security gateway 1  400 &#39;s network interface. Packet security gateway 1  400  may apply one or more of the rules in P 1  to the received packet until the packet matches criteria specified by a rule in P 1 , at which point packet security gateway 1  400  may perform a packet transformation function specified by the rule on the packet. For example, a packet may be received by packet security gateway  112  that originates from external host E 5  (e.g., a host within network E  110 ) and is destined for internal host I 7  (e.g., a host within network A  102 ). Packet security gateway 1  400  may apply one or more of the rules in P 1  (e.g., {{E 1 }, {E 2 }, . . . , {E M }}) to the received packet and the received packet may match the criteria specified by one of the rules in P 1  (e.g., {{E 5 }). The rule may specify that an accept packet transformation function should be performed, and packet security gateway 1  400  may utilize one or more of its packet transformation functions to perform the accept packet transformation function on the packet and forward the packet to packet security gateway 2  402 . Packet security gateway 2  402  may apply one or more of the rules in P 2  (e.g., {{I 1 }, {I 2 }, . . . , {I N }}) to the packet and the packet may match the criteria specified by one of the rules in P 2  (e.g., {{I 7 }). The rule may specify that an accept packet transformation function should be performed, and packet security gateway 2  402  may utilize one or more of its packet transformation functions to perform the accept packet transformation function on the packet and forward the packet to network A  102 . 
     It will be appreciated that utilizing multiple packet security gateways in series to implement dynamic security policy constructs may increase performance and decrease memory resource requirements. For example, in the described scenario packet security gateway 1  400  may have only been required to compare the packet to five rules and packet security gateway 2  402  may have only been required to compare the packet to seven rules. In a worst case scenario, packet security gateway 1  400  may have only been required to compare the packet to M rules and packet security gateway 2  402  may have only been required to compare the packet to N rules. Moreover, the series configuration may enable packet security gateway 1  400  to begin implementing P 1  with respect to a subsequently received packet, while packet security gateway 2  402  simultaneously implements P 2  with respect to the packet forwarded by packet security gateway 1  400 . Furthermore, the memory requirements for this scenario with packet security gateways in series may be comparable to M+N, whereas originally the combinatorially complete set of rules contained in a single packet security gateway may have required memory comparable to N*M. 
       FIG. 5  illustrates an exemplary security policy management server. Referring to  FIG. 5 , security policy management server  120  may include processor  500 , memory  502 , and network interface  504 . One or more of processor  500 , memory  502 , and network interface  504  may be interconnected via data bus  506 . Network interface  504  may interface security policy management server  120  with network E  110 . Memory  502  may include one or more program modules that when executed by processor  500 , configure security policy management server  120  to perform functions described herein. It will be appreciated that as used herein the term “server” designates one or more computing devices configured to perform one or more functions described herein. The term “server” should not be construed to imply that a client/server relationship (e.g., a relationship in which a request is received from a client and then serviced by a server) necessarily exists. 
     Security policy management server  120  may be configured to communicate one or more dynamic security policies to one or more packet security gateways within network environment  100 . For example, security policy management server  120  may communicate one or more dynamic security policies stored in memory  502  to one or more of packet security gateways  112 ,  114 ,  116 , and  118 . For example, security policy management server  120  may be configured to communicate one or more dynamic security policies to one or more of packet security gateways  112 ,  114 ,  116 , and  118  on a periodic basis, under specified network conditions, whenever security policy management server  120  receives a new dynamic security policy, whenever a dynamic security policy stored on security policy management server  120  is changed or altered, or in response to a request from one or more of packet security gateways  112 ,  114 ,  116 , and  118 . 
     Security policy management server  120  may also be configured to provide one or more administrators associated with security policy management server  120  with management interface  510 . For example, security policy management server  120  may be configured to provide one or more administrators with a Graphical User Interface (GUI) or Command Line Interface (CLI). An administrator of security policy management server  120  may utilize security policy management server  120 &#39;s management interface  510  to configure security policy management server  120 . For example, an administrator may configure security policy management server  120  in order to associate security policy management server  120  with one or more of packet security gateways  112 ,  114 ,  116 , and  118 . An administrator of security policy management server  120  may also utilize security policy management server  120 &#39;s management interface  510  to construct one or more dynamic security policies or to load one or more dynamic security policies into security policy management server  120 &#39;s memory  502 . For example, an administrator associated with security policy management server  120  may manually construct one or more dynamic security policies offline and then utilize security policy management server  120 &#39;s management interface  510  to load such dynamic security policies into security policy management server  120 &#39;s memory  502 . 
     In some embodiments, security policy management server  120  may be configured to add, remove, or alter one or more dynamic security policies stored in memory  502  based on information received from one or more devices within network environment  100 . For example, security policy management server  120 &#39;s memory  502  may include a dynamic security policy having one or more rules that specify a list of network addresses known to be associated with malicious network traffic. Security policy management server  120  may be configured to automatically create or alter one or more of such rules as new network addresses associated with malicious network traffic are determined. For example, security policy management server  120  may receive updates (e.g. as part of a subscription) from malicious host tracker service  508 . Malicious host tracker service  508  may aggregate information associated with malicious network traffic and updates received from malicious host tracker service  508  may include one or more network addresses that have been determined to be associated with malicious network traffic. Security policy management server  120  may be configured to create or alter one or more rules included within a dynamic security policy associated with malicious host tracker service  508  to block traffic associated with the network addresses received from malicious host tracker service  508 . Additionally or alternatively, as indicated above, security policy management server  120  may be configured to create or alter one or more dynamic security policies, or one or more rules included in one or more dynamic security policies, to account for VoIP sessions being initiated or terminated by a network device within network environment  100 . 
     As indicated above, a dynamic security policy may include one or more rules, the combination of which may effectuate an implementation of a multi-dimensional routing service for performing a monitoring service within a network environment.  FIG. 6  illustrates an exemplary network environment for implementing a monitoring service in accordance with one or more embodiments. Referring to  FIG. 6 , a user of network environment  100  (e.g., a law enforcement or national security authority) may desire to obtain a copy of packets associated with one or more VoIP sessions (e.g., sessions associated with SIP URI exampleuser@exampledomain.com) within network environment  100 . Because many SIP-signaled services are designed to address sessions dynamically, it may not be possible to determine, prior to a session being set up, a particular network address and port from which packets should be copied. Moreover, due to privacy concerns, regulators may require that only packets associated with the specified VoIP sessions (e.g., sessions associated with SIP URI exampleuser@exampledomain.com) be copied. 
     For example, a user associated with SIP URI exampleuser@exampledomain.com may utilize User Equipment (UE)  600  within network A  102  to place a VoIP call to a user utilizing UE  602  within network B  104 . SIP switch  604  may be utilized by an operator of network A  102  for switching SIP signals within network A  102 . Similarly, SIP switch  606  may be utilized by an operator of network B  104  for switching SIP signals within network B  104 . One or more of SIP switches  604  and  606  may include an analysis application configured to monitor SIP signals and publish SIP messages associated with specified users to one or more subscribers. For example, the operator of network A  102  may have installed analysis application  610  on SIP switch  604  (e.g., accessed via a SIP IMS Service Control (ISC) interface associated with SIP switch  604 ) and configured analysis application  610  to search for and publish SIP messages associated with SIP URI exampleuser@exampledomain.com to security policy management server  120 . Similarly, the operator of network B  104  may have installed analysis application  612  on SIP switch  606  and configured analysis application  612  to publish SIP messages associated with SIP URI exampleuser@exampledomain.com to security policy management server  120 . 
     When the user associated with SIP URI exampleuser@exampledomain.com utilizes UE  600  to place a VoIP call to the user utilizing UE  602 , analysis application  610  may detect one or more SIP signaling messages associated with the call (e.g., SIP signaling messages for setting up the call) and publish the messages to security policy management server  120 . Security policy management server  120  may extract one or more network addresses and port numbers from the SIP signaling messages (e.g., a network address and port number utilized by UE  600  for placing the VoIP call to UE  602 ). Security policy management server  120  may utilize the extracted network addresses and port numbers to create a new dynamic security policy or alter one or more rules within an existing dynamic security policy. For example, security policy management server  120  may construct a new dynamic security policy that includes a rule specifying one of the extracted network addresses and port numbers, as well as a packet transformation function configured to route associated packets to monitoring device  608 . Security policy management server  120  may communicate the new or modified dynamic security policy to packet security gateway  112 . 
     When packets associated with the VoIP call between UE  600  and UE  602  are received by packet security gateway  112 , packet filter  214  may identify the packets as matching the criteria specified by the dynamic security policy received from security policy management server  120  (e.g., packets addressed to or from the extracted address and port number) and may perform the packet transformation function configured to route the packets to monitoring device  608 . For example, the packet transformation function configured to route the packets to monitoring device  608  may be packet transformation function 2  218 . When packet transformation function 2  218  receives the packets from packet filter  214 , it may encapsulate them with an IP header having an address corresponding to monitoring device  608  and may then forward them to network E  110 . Once forwarded, the packets may be routed based on the address specified by the encapsulating header, and may thus be communicated to monitoring device  608 . When the packets are received by monitoring device  608 , monitoring device  608  may copy the packets or data contained within them, and strip the encapsulating header from them. Monitoring device  608  may then forward the packets, without the encapsulating header, to network E  110 . Network E  110  may receive the packets forwarded by monitoring device  608  and may route them based on their destination address (e.g., to UE  602 ). 
     In some embodiments, packet security gateway  112  may be configured to perform multiple packet transformation functions on the packets associated with the VoIP call between UEs  600  and  602 . For example, packet filter  214  may identify the packets as matching the criteria specified by the dynamic security policy received from security policy management server  120  and may forward the packets to packet transformation functions 1  216  and 2  218 . Packet transformation function 1  216  may be configured to forward the packets to their destination address (e.g., to UE  602 ) and packet transformation function 2  218  may be configured to encapsulate the packets (or a copy of the packets) with an IP header having an address corresponding to monitoring device  608  and then forward the encapsulated packets to network E  110 . Once forwarded, the encapsulated packets may be routed based on the address specified by the encapsulating header, and may thus be communicated to monitoring device  608 , which may store the packets or data contained within them for subsequent review or analysis (e.g., by a law enforcement or national security authority). In such embodiments, it may not be necessary for monitoring device  608  to strip the encapsulating header from the packets or route them based on their destination address (e.g., to UE  602 ) because packet transformation function 1  216  may have already forwarded the packets to their destination address (e.g., to UE  602 ). 
     It will be appreciated that SIP switch  604 &#39;s analysis application  610  may similarly detect SIP signaling associated with the termination of the VoIP call between UE  600  and UE  602  and may publish the SIP messages to security policy management server  120 . Security policy management server  120  may utilize one or more network addresses and port numbers within the messages to construct a new dynamic security policy or modify one or more rules within an existing dynamic security policy and communicate the new or modified dynamic security policy to packet security gateway  112  in order to ensure that future packets associated with the network address and port number but not associated with SIP URI exampleuser@exampledomain.com are not routed to monitoring device  608 . Security policy management server  120  may communicate any dynamic security policy constructed or modified based on SIP messages to any of multiple packet security gateways (e.g., packet security gateways  114  and  116 ) within network environment  100  in order to ensure that all packets associated with the VoIP call between UE  600  and UE  602  are forwarded to monitoring device  608 . 
       FIG. 7  illustrates an exemplary network environment that includes a secured network having multiple boundaries with unsecured networks in which one or more embodiments may be implemented. Network environment  700  may include networks A-C  702 ,  704 , and  706 . Networks A  702  and B  704  may be a LAN or WAN associated with an organization (e.g., a company, university, enterprise, or government agency). One or more networks within network environment  700  may interface with one or more other networks within network environment  700 . For example, the organizations associated with networks A  702  and B  704  may subscribe to an ISP to provide interconnectivity between their respective networks or allow public access to their respective networks (e.g., via the Internet). Each of networks A  702  and B  704  may be connected to network C  706 , which may be the ISP&#39;s network. The ISP may desire to offer an interconnection service between networks A  702  and B  704 , but may also want to enforce one or more dynamic security policies with respect to traffic traversing network C  706 . Accordingly, one or more packet security gateways may be located at each boundary between network A  702  and network C  706 , and each boundary between network B  704  and network C  706 . For example, packet security gateway  708  and packet security gateway  710  may be respectively located at first and second boundaries between networks A  702  and C  706 . Similarly, packet security gateways  712  and  714  may be respectively located at first and second boundaries between networks B  704  and C  706 . Each of packet security gateways  708 ,  710 ,  712 , and  714  may be associated with security policy management server  716 . 
     Security policy management server  716  may maintain one or more dynamic security policies configured for protecting network C  706 , and may be managed by the ISP associated with network C  706 . Security policy management server  716  may ensure that each of packet security gateways  708 ,  710 ,  712 , and  714  protect each of their respective boundaries with network C  706  in a uniform manner. For example, security policy management server  716  may be configured to communicate one or more dynamic security policies it maintains to each of packet security gateways  708 ,  710 ,  712 , and  714  on a periodic basis, in response to being directed to by a network operator associated with network environment  700 , in response to detected network conditions (e.g., an attack or high resource utilization), or in response to a request from one or more of packet security gateways  708 ,  710 ,  712 , or  714 . 
     In some embodiments, security policy management server  716  may be configured to communicate different dynamic security policies to one or more of packet security gateways  708 ,  710 ,  712 , and  714  based on, for example, their respective locations within network environment  700 . For example, security policy management server  716  may be configured to implement one or more anti-spoofing techniques (e.g., ingress filtering or Best Current Practice (BCP)  38 , as described by Internet Engineering Task Force (IETF) Request For Comment (RFC)  2827 ) with respect to network environment  700 . Effective implementation of such techniques may require that a dynamic security policy be based on the location at which it is being implemented. For example, a dynamic security policy that implements ingress filtering may comprise one or more rules that filter based on a packet&#39;s source address, identifying packets having source addresses that could not possibly have originated from a network downstream of the ingress filtering point (e.g., packets having spoofed source addresses). Such rules may vary depending on the boundary point for which they are implemented (e.g., a packet for one boundary may be properly identified as spoofed, yet a packet having the same source address may be legitimate traffic at a different boundary point). Accordingly, security policy management server  716  may be configured to communicate different dynamic security policies to one or more of packet security gateways  708 ,  710 ,  712 , and  714  based on their respective locations within network environment  700 . For example, security policy management server  716  may communicate a dynamic security policy to packet security gateways  708  and  710  that includes one or more rules for performing ingress filtering for network A  702  (e.g., for identifying packets having source addresses that could not have originated within network A  702 ) and a different dynamic security policy to packet security gateways  712  and  714  that includes one or more rules for performing ingress filtering for network B  704  (e.g., for identifying packets having source addresses that could not have originated within network B  704 ). 
     It will be appreciated that by maintaining uniform dynamic security policies at each boundary between networks A  702  and C  706 , as well as at each boundary between networks B  704  and C  706 , security policy management server  716  and packet security gateways  708 ,  710 ,  712 , and  714  may aid the ISP associated with network C  706  in protecting network C  706  from network attacks. 
       FIG. 8  illustrates an exemplary network environment that includes multiple distinct secured networks in which one or more embodiments may be implemented. Referring to  FIG. 8 , network environment  800  may include networks A  802 , B  804 , and C  806 . Each of networks A  802  and B  804  may interface with network C  806  at multiple boundaries within network environment  800 . Packet security gateways  808  and  810  may be respectively located at first and second boundaries between networks A  802  and C  806 . Similarly, packet security gateways  812  and  814  may be respectively located at first and second boundaries between networks B  804  and C  806 . 
     Network A  802  and B  804  may both be associated with a common organization (e.g., a company, university, enterprise, or government agency), or may each be associated with a distinct organization. In the former case, the common organization may desire to utilize one or more dynamic security policies with respect to network A  802  and one or more different dynamic security policies with respect to network B  804 . In the latter case, an organization associated with network A  802  may desire to utilize one or more dynamic security policies with respect to network A  802  and a different organization associated with network B  804  may desire to utilize one or more different dynamic security policies with respect to network B  804 . Network environment  800  may include security policy management servers A  816  and B  818 . Security policy management server A  816  may be associated with network A  802  and may maintain one or more dynamic security policies configured for protecting network A  802 . Similarly, security policy management server B  818  may be associated with network B  804  and may maintain one or more dynamic security policies configured for protecting network B  804 . 
     Packet security gateways  808  and  810  may be associated with security policy management server A  816 . Similarly, packet security gateways  812  and  814  may be associated with security policy management server B  818 . Security policy management server A  816  may ensure that packet security gateways  808  and  810  protect each of their respective boundaries with network C  806  in a uniform manner. For example, security policy management server A  816  may be configured to communicate one or more dynamic security policies it maintains to packet security gateways  808  and  810  on a periodic basis, in response to being directed to by a network operator associated with network A  802 , in response to detected network conditions (e.g., an attack or high resource utilization), or in response to a request from packet security gateway  808  or  810 . Similarly, security policy management server B  818  may ensure that packet security gateways  812  and  814  protect each of their respective boundaries with network C  806  in a uniform manner. For example, security policy management server B  818  may be configured to communicate one or more dynamic security policies it maintains to packet security gateways  812  and  814  on a periodic basis, in response to being directed to by a network operator associated with network B  804 , in response to detected network conditions (e.g., an attack or high resource utilization), or in response to a request from packet security gateway  812  or  814 . By utilizing distinct security policy management servers (e.g., security policy management servers A  816  and B  818 ), one or more operators associated with distinct networks (e.g., networks A  802  and B  804 ) may maintain uniform dynamic security policies at each boundary of their respective networks, while simultaneously enabling different dynamic security policies to be maintained for each network. Similarly, by utilizing distinct security policy management servers (e.g., security policy management servers A  816  and B  818 ), one or more operators associated with a single organization that desires to maintain distinct networks (e.g., networks A  802  and B  804 ) may maintain uniform dynamic security policies at each boundary of their distinct networks, while simultaneously enabling different dynamic security policies to be maintained for each network. 
       FIG. 9  illustrates an exemplary secure LAN environment protected in accordance with one or more aspects of the disclosure. Referring to  FIG. 9 , network environment  900  may be a LAN, including hosts A  902 , B  904 , and C  906 . It may also include LAN switch  908 . LAN switch  908  may be configured to switch network traffic (e.g., packets) between one or more of hosts A  902 , B  904 , and C  906 . For example, LAN switch  908  may include a switching matrix configured to switch packets received from one or more of hosts A  902 , B  904 , and C  906  to one or more of hosts A  902 , B  904 , and C  906 . LAN switch  908  may be associated with packet security gateway  910 , and network environment  900  may include security policy management server  912 . 
     In some embodiments, packet security gateway  910  may be embedded within LAN switch  908 . Alternatively, packet security gateway  910  may be a device distinct from LAN switch  908 , and LAN switch  908  may be configured to route network traffic through packet security gateway  910  (e.g., by modifying LAN switch  908 &#39;s switching matrix). Packet security gateway  910  may be configured to receive one or more dynamic security policies from security policy management server  912 . The dynamic security policies received from security policy management server  912  may include one or more rules specifying criteria associated with one or more of hosts A  902 , B  904 , and C  906 , and may further specify one or more packet transformation functions to be performed on packets matching the specified criteria. Packet security gateway  910  may identify packets matching one or more of the criteria specified by the rules and may perform the associated packet transformation functions on the identified packets. By utilizing packet security gateway  910  within network environment  900 , an operator of network environment  900  may be able to protect network environment  900  from network attacks, as well as implement one or more services (e.g., blocklist service, allowlist service, VoIP firewall service, phased restoration service, enqueueing service, multi-dimensional routing service, or monitoring service) within network environment  900 . Network environment  900  may include multiple LAN switches with embedded or associated packet security gateways, each of the packet security gateways configured to receive one or more dynamic security policies from security policy management server  912 . 
       FIG. 10  illustrates an exemplary method for protecting a secured network in accordance with one or more embodiments. The steps may be performed at each of one or more packet security gateways associated with a security policy management server. For example, each of packet security gateways  112 ,  114 ,  116 , and  118  may be associated with security policy management server  120 , and the steps may be performed at each of packet security gateways  112 ,  114 ,  116 , and  118 . At step  1000 , a dynamic security policy is received from the security policy management server. For example, packet security gateway  112  may receive dynamic security policy  300  from security policy management server  120 . At step  1002 , packets associated with a network protected by each respective packet security gateway are received. For example, packet security gateway  112  may receive UDP packets from a device within network E  110  having an address that begins with 150 and that are destined for port 3030 of a device within network A  102 . At step  1004 , a packet transformation function specified by the dynamic security policy is performed on the packets. For example, rule  308  of dynamic security policy  300  may specify that packets using the UDP protocol, coming from a source address that begins with 150, having any source port, destined for any address, and destined for port 3030 should have an accept packet transformation function performed on them, packet filter  214  may identify the UDP packets received from the device within network E  110  as matching the criteria specified by rule  308 , packet transformation function 1  216  may be configured to forward packets, and packet security gateway  112  may utilize packet transformation function 1  216  to perform the accept packet transformation function specified by rule  308  on the UDP packets received from the device within network E  110 . 
     The functions and steps described herein may be embodied in computer-usable data or computer-executable instructions, such as in one or more program modules, executed by one or more computers or other devices to perform one or more functions described herein. Generally, program modules include routines, programs, objects, components, data structures, etc. that perform particular tasks or implement particular abstract data types when executed by one or more processors in a computer or other data processing device. The computer-executable instructions may be stored on a computer-readable medium such as a hard disk, optical disk, removable storage media, solid state memory, RAM, etc. As will be appreciated, the functionality of the program modules may be combined or distributed as desired in various embodiments. In addition, the functionality may be embodied in whole or in part in firmware or hardware equivalents, such as integrated circuits, application-specific integrated circuits (ASICs), field programmable gate arrays (FPGA), and the like. Particular data structures may be used to more effectively implement one or more aspects of the disclosure, and such data structures are contemplated to be within the scope of computer executable instructions and computer-usable data described herein. 
     Although not required, one of ordinary skill in the art will appreciate that various aspects described herein may be embodied as a method, an apparatus, or as one or more computer-readable media storing computer-executable instructions. Accordingly, those aspects may take the form of an entirely hardware embodiment, an entirely software embodiment, an entirely firmware embodiment, or an embodiment combining software, hardware, and firmware aspects in any combination. 
     As described herein, the various methods and acts may be operative across one or more computing servers and one or more networks. The functionality may be distributed in any manner, or may be located in a single computing device (e.g., a server, a client computer, etc.). 
     Aspects of the disclosure have been described in terms of illustrative embodiments thereof. Numerous other embodiments, modifications, and variations within the scope and spirit of the appended claims will occur to persons of ordinary skill in the art from a review of this disclosure. For example, one of ordinary skill in the art will appreciate that the steps illustrated in the illustrative figures may be performed in other than the recited order, and that one or more steps illustrated may be optional.