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BGP hijacking (sometimes referred to as prefix hijacking, route hijacking or IP hijacking) is the illegitimate takeover of groups of IP addresses by corrupting Internet routing tables maintained using the Border Gateway Protocol (BGP). [1] [2] [3] [4] [5]
The Internet is a global network that enables any connected host, identified by its unique IP address, to talk to any other, anywhere in the world. This is achieved by passing data from one router to another, repeatedly moving each packet closer to its destination, until it is delivered. To do this, each router must be regularly supplied with up-to-date routing tables. At the global level, individual IP addresses are grouped together into prefixes. These prefixes will be originated, or owned, by an autonomous system (AS), and the routing tables between ASes are maintained using the Border Gateway Protocol (BGP).
A group of networks that operates under a single external routing policy is known as an autonomous system. For example, Sprint, Verizon, and AT&T each are an AS. Each AS has its own unique AS identifier number. BGP is the standard routing protocol used to exchange information about IP routing between autonomous systems.
Each AS uses BGP to advertise prefixes that it can deliver traffic to. For example, if the network prefix 192.0.2.0/24 is inside AS 64496, then that AS will advertise to its provider(s) and/or peer(s) that it can deliver any traffic destined for 192.0.2.0/24.
Although security extensions are available for BGP, and third-party route DB resources exist for validating routes, by default the BGP protocol is designed to trust all route announcements sent by peers. Few ISPs rigorously enforce checks on BGP sessions.
IP hijacking can occur deliberately or by accident in one of several ways:
Common to these ways is their disruption of the normal network routing: packets end up being forwarded towards the wrong part of the network and then either enter an endless loop (and are discarded), or are found at the mercy of the offending AS.
Typically ISPs filter BGP traffic, allowing BGP advertisements from their downstream networks to contain only valid IP space. However, a history of hijacking incidents shows this is not always the case.
The Resource Public Key Infrastructure (RPKI) is designed to authenticate route origins via cryptographic certificate chains demonstrating address block range ownership but is not widely deployed yet. Once deployed, IP hijacking through errant issues at the origin (via accident or intent) should be detectable and filterable.
IP hijacking is sometimes used by malicious users to obtain IP addresses for use in spamming or a distributed denial-of-service (DDoS) attack.
When a router promulgates flawed BGP routing information, whether that action is intentional or accidental, it is defined by the Internet Engineering Task Force (IETF) in RFC 7908 as a "route leak". Such leaks are described as "the propagation of routing announcement(s) beyond their intended scope. That is, an announcement from an Autonomous System (AS) of a learned BGP route to another AS violates the intended policies of the receiver, the sender, and/or one of the ASes along the preceding AS path." Such leaks are possible because of a long-standing "…systemic vulnerability of the Border Gateway Protocol routing system…" [6]
Like the TCP reset attack, session hijacking involves intrusion into an ongoing BGP session, i.e., the attacker successfully masquerades as one of the peers in a BGP session, and requires the same information needed to accomplish the reset attack. The difference is that a session hijacking attack may be designed to achieve more than simply bringing down a session between BGP peers. For example, the objective may be to change routes used by the peer, in order to facilitate eavesdropping, black holing, or traffic analysis.
By default EBGP peers will attempt to add all routes received by another peer into the device's routing table and will then attempt to advertise nearly all of these routes to other EBGP peers. This can be a problem as multi-homed organizations can inadvertently advertise prefixes learned from one AS to another, causing the end customer to become the new, best-path to the prefixes in question. For example, a customer with a Cisco router peering with say AT&T and Verizon and using no filtering will automatically attempt to link the two major carriers, which could cause the providers to prefer sending some or all traffic through the customer (on perhaps a T1), instead of using high-speed dedicated links. This problem can further affect others that peer with these two providers and also cause those ASs to prefer the misconfigured link. In reality, this problem hardly ever occurs with large ISPs, as these ISPs tend to restrict what an end customer can advertise. However, any ISP not filtering customer advertisements can allow errant information to be advertised into the global routing table where it can affect even the large Tier-1 providers.
The concept of BGP hijacking revolves around locating an ISP that is not filtering advertisements (intentionally or otherwise) or locating an ISP whose internal or ISP-to-ISP BGP session is susceptible to a man-in-the-middle attack. Once located, an attacker can potentially advertise any prefix they want, causing some or all traffic to be diverted from the real source towards the attacker. This can be done either to overload the ISP the attacker has infiltrated, or to perform a DoS or impersonation attack on the entity whose prefix is being advertised. It is not uncommon for an attacker to cause serious outages, up to and including a complete loss of connectivity. In early 2008, at least eight US Universities had their traffic diverted to Indonesia for about 90 minutes one morning in an attack kept mostly quiet by those involved.[ citation needed ] Also, in February 2008, a large portion of YouTube's address space was redirected to Pakistan when the PTA decided to block access [7] to the site from inside the country, but accidentally blackholed the route in the global BGP table.
While filtering and MD5/TTL protection is already available for most BGP implementations (thus preventing the source of most attacks), the problem stems from the concept that ISPs rarely ever filter advertisements from other ISPs, as there is no common or efficient way to determine the list of permissible prefixes each AS can originate. The penalty for allowing errant information to be advertised can range from simple filtering by other/larger ISPs to a complete shutdown of the BGP session by the neighboring ISP (causing the two ISPs to cease peering), and repeated problems often end in permanent termination of all peering agreements. It is also noteworthy that even causing a major provider to block or shutdown a smaller, problematic provider, the global BGP table will often reconfigure and reroute the traffic through other available routes until all peers take action, or until the errant ISP fixes the problem at the source.
One useful offshoot of this concept is called BGP anycasting and is frequently used by root DNS servers to allow multiple servers to use the same IP address, providing redundancy and a layer of protection against DoS attacks without publishing hundreds of server IP addresses. The difference in this situation is that each point advertising a prefix actually has access to the real data (DNS in this case) and responds correctly to end user requests.
A router is a networking device that forwards data packets between computer networks. Routers perform the traffic directing functions between networks and on the global Internet. Data sent through a network, such as a web page or email, is in the form of data packets. A packet is typically forwarded from one router to another router through the networks that constitute an internetwork until it reaches its destination node.
Border Gateway Protocol (BGP) is a standardized exterior gateway protocol designed to exchange routing and reachability information among autonomous systems (AS) on the Internet. BGP is classified as a path-vector routing protocol, and it makes routing decisions based on paths, network policies, or rule-sets configured by a network administrator.
In computer networking, peering is a voluntary interconnection of administratively separate Internet networks for the purpose of exchanging traffic between the "down-stream" users of each network. Peering is settlement-free, also known as "bill-and-keep" or "sender keeps all", meaning that neither party pays the other in association with the exchange of traffic; instead, each derives and retains revenue from its own customers.
A Tier 1 network is an Internet Protocol (IP) network that can reach every other network on the Internet solely via settlement-free interconnection. Tier 1 networks can exchange traffic with other Tier 1 networks without paying any fees for the exchange of traffic in either direction. In contrast, some Tier 2 networks and all Tier 3 networks must pay to transmit traffic on other networks.
In computer networking, a proxy server is a server application that acts as an intermediary between a client requesting a resource and the server providing that resource. It improves privacy, security, and performance in the process.
Network mapping is the study of the physical connectivity of networks e.g. the Internet. Network mapping discovers the devices on the network and their connectivity. It is not to be confused with network discovery or network enumerating which discovers devices on the network and their characteristics such as. The field of automated network mapping has taken on greater importance as networks become more dynamic and complex in nature.
A virtual private network (VPN) is a mechanism for creating a secure connection between a computing device and a computer network, or between two networks, using an insecure communication medium such as the public Internet.
An autonomous system (AS) is a collection of connected Internet Protocol (IP) routing prefixes under the control of one or more network operators on behalf of a single administrative entity or domain, that presents a common and clearly defined routing policy to the Internet. Each AS is assigned an autonomous system number (ASN), for use in Border Gateway Protocol (BGP) routing. Autonomous System Numbers are assigned to Local Internet Registries (LIRs) and end user organizations by their respective Regional Internet Registries (RIRs), which in turn receive blocks of ASNs for reassignment from the Internet Assigned Numbers Authority (IANA). The IANA also maintains a registry of ASNs which are reserved for private use.
Anycast is a network addressing and routing methodology in which a single IP address is shared by devices in multiple locations. Routers direct packets addressed to this destination to the location nearest the sender, using their normal decision-making algorithms, typically the lowest number of BGP network hops. Anycast routing is widely used by content delivery networks such as web and name servers, to bring their content closer to end users.
Deep packet inspection (DPI) is a type of data processing that inspects in detail the data being sent over a computer network, and may take actions such as alerting, blocking, re-routing, or logging it accordingly. Deep packet inspection is often used for baselining application behavior, analyzing network usage, troubleshooting network performance, ensuring that data is in the correct format, checking for malicious code, eavesdropping, and internet censorship, among other purposes. There are multiple headers for IP packets; network equipment only needs to use the first of these for normal operation, but use of the second header is normally considered to be shallow packet inspection despite this definition.
Multihoming is the practice of connecting a host or a computer network to more than one network. This can be done in order to increase reliability or performance.
A route distinguisher is an address qualifier used only within a single internet service provider's Multiprotocol Label Switching (MPLS) network. It is used to distinguish the distinct virtual private network (VPN) routes of separate customers who connect to the provider.
A supernetwork, or supernet, is an Internet Protocol (IP) network that is formed by aggregation of multiple networks into a larger network. The new routing prefix for the aggregate network represents the constituent networks in a single routing table entry. The process of forming a supernet is called supernetting, prefix aggregation, route aggregation, or route summarization.
An overlay network is a computer network that is layered on top of another network. The concept of overlay networking is distinct from the traditional model of OSI layered networks, and almost always assumes that the underlay network is an IP network of some kind.
The Toronto Internet Exchange Community (TorIX) is a not-for-profit Internet Exchange Point (IXP) located in a carrier hotel at 151 Front Street West, Equinix's TR2 data centre at 45 Parliament Street and 905 King Street West in Toronto, Ontario, Canada. As of March 2021, TorIX has 259 unique autonomous systems representing 285 peer connections and peak traffic rates of 1.344 Tbps, making it the largest IXP in Canada. According to Wikipedia's List of Internet Exchange Points by Size, TorIX is the 16th largest IXP in the world in numbers of peers, and 17th in the world in traffic averages. The Exchange is organized and run by industry professionals in voluntary capacity.
In computer networking, ingress filtering is a technique used to ensure that incoming packets are actually from the networks from which they claim to originate. This can be used as a countermeasure against various spoofing attacks where the attacker's packets contain fake IP addresses. Spoofing is often used in denial-of-service attacks, and mitigating these is a primary application of ingress filtering.
In Internet routing, the default-free zone (DFZ) is the collection of all Internet autonomous systems (AS) that do not require a default route to route a packet to any destination. Conceptually, DFZ routers have a "complete" Border Gateway Protocol table, sometimes referred to as the Internet routing table, global routing table or global BGP table. However, internet routing changes rapidly and the widespread use of route filtering ensures that no router has a complete view of all routes. Any routing table created would look different from the perspective of different routers, even if a stable view could be achieved.
In the context of network routing, route filtering is the process by which certain routes are not considered for inclusion in the local route database, or not advertised to one's neighbours. Route filtering is particularly important for the Border Gateway Protocol on the global Internet, where it is used for a variety of reasons. One way of doing route filtering with external-resources in practice is using Routing Policy Specification Language in combination with Internet Routing Registry databases.
DNS hijacking, DNS poisoning, or DNS redirection is the practice of subverting the resolution of Domain Name System (DNS) queries. This can be achieved by malware that overrides a computer's TCP/IP configuration to point at a rogue DNS server under the control of an attacker, or through modifying the behaviour of a trusted DNS server so that it does not comply with internet standards.
Resource Public Key Infrastructure (RPKI), also known as Resource Certification, is a specialized public key infrastructure (PKI) framework to support improved security for the Internet's BGP routing infrastructure.