Deep packet inspection

From Wikipedia, the free encyclopedia

Deep Packet Inspection (DPI) is the act of any IP network equipment which is not an endpoint of a communication using any field other than the layer 3 destination IP address for any purpose. This is performed as the packet passes an inspection point, searching for protocol non-compliance, viruses, spam, intrusions or predefined criteria to decide what actions to take on the packet, including collecting statistical information. This is in contrast to shallow packet inspection (usually called Stateful Packet Inspection) which just checks the header portion of a packet.^[1]

Deep Packet Inspection (and filtering) enables advanced security functions as well as internet data mining, eavesdropping, and censorship. Advocates of net neutrality fear that DPI technology will be used to reduce the openness of the Internet. DPI is currently being used by the enterprise, service providers and governments in a wide range of applications.

Contents 1 Background 2 Deep Packet Inspection at the enterprise 3 Deep Packet Inspection at Internet service providers 3.1 Lawful intercept 3.2 Policy definition and enforcement 3.3 Targeted advertising 3.4 Quality of service 3.5 Tiered services 3.6 Copyright enforcement 4 Deep Packet Inspection by governments 4.1 United States 4.2 China 4.3 Iran 5 DPI and net neutrality 6 See also 7 References 8 External links

[edit] Background

Deep Packet Inspection (DPI) combines the functionality of an Intrusion Detection System (IDS) and an Intrusion Prevention System (IPS) with a traditional stateful firewall.^[2] This combination makes it possible to detect certain attacks that neither the IDS/IPS nor the stateful firewall can catch on their own. Stateful firewalls, while able to see the beginning and end of a packet flow, cannot on their own catch events that would be out of bounds for a particular application. While IDSs are able to detect intrusions, they have very little capability in blocking such an attack. DPIs are used to prevent attacks from viruses and worms at wire speeds. More specifically, DPI can be effective against buffer overflow attacks, Denial of Service (DoS) attacks, sophisticated intrusions, and a small percentage of worms that fit within a single packet.

DPI devices have the ability to look at Layer 2 through Layer 7 of the OSI model. This includes headers and data protocol structures as well as the actual payload of the message. The DPI will identify and classify the traffic based on a signature database that includes information extracted from the data part of a packet, allowing finer control than classification based only on header information.

DPI is a required technology for Network Address Translation (NAT), in residential, enterprise, and service provider networks. In this context, it provides what the IETF calls an Application Level Gateway.

A classified packet can be redirected, marked/tagged (see quality of service), blocked, rate limited, and of course reported to a reporting agent in the network. In this way, HTTP errors of different classifications may be identified and forwarded for analysis. Many DPI devices can identify packet flows (rather than packet-by-packet analysis), allowing control actions based on accumulated flow information.

[edit] Deep Packet Inspection at the enterprise

Until recently security at the enterprise was just a perimeter discipline, with a dominant philosophy of keeping unauthorized users out, and shielding authorized users from the outside world. The most frequently used tool for accomplishing this has been a stateful firewall. It can permit fine-grained control of access from the outside world to pre-defined destinations on the internal network, as well as permitting access back to other hosts only if a request to the outside world has been made previously.^[3]

However, vulnerabilities exist at network layers that are not visible to a stateful firewall. Also, an increase in the use of laptops in the enterprise makes it more difficult to prevent threats such as viruses, worms and spyware from penetrating the corporate network, as many users will connect the laptop to less-secure networks such as home broadband connections or wireless networks in public locations. Firewalls also do not distinguish between permitted and forbidden uses of legitimately-accessed applications. DPI enables IT administrators and security officials to set policies and enforce them at all layers, including the application and user layer to help combat those threats.

Deep Packet Inspection is able to detect a few kinds of buffer overflow attacks.

[edit] Deep Packet Inspection at Internet service providers

In addition to using DPI to secure their internal networks, Internet service providers also apply this technology on the public networks provided to customers. Common uses of DPI by ISPs are lawful intercept, policy definition and enforcement, targeted advertising, quality of service, offering tiered services, and copyright enforcement.

[edit] Lawful intercept

Service providers are required by various governments around the world and their agencies to allow lawful intercept capabilities. This had been previously met by creating a traffic access point (TAP) using an intercepting proxy server that connects to the government's surveillance equipment. Now that this functionality can be included in the DPI, DPI products that are "CALEA-compliant" can be used as a TAP to collect a user's datastream.^[4]

[edit] Policy definition and enforcement

Service providers obligated by the service level agreement with their customers to provide a certain level of service, and at the same time enforce an acceptable use policy, may make use of DPI to implement certain policies that cover copyright infringements, illegal materials, and unfair use of bandwidth. In some countries the ISPs are required to perform filtering depending on the country's laws. DPI allows service providers to "readily know the packets of information you are receiving online—from e-mail, to websites, to sharing of music, video and software downloads".^[5] Policies can be defined that allow or disallow connection to or from an IP address, certain protocols, or even heuristics that identify a certain application or behavior.

[edit] Targeted advertising

Because ISPs route all of their customers' traffic, they are able to monitor web-browsing habits in a very detailed way allowing them to gain information about their customers' interests, which can be used by companies specializing in targeted advertising. At least 100,000 US customers are tracked this way, and as many of 10% of US customers have been tracked in this way. Technology providers include NebuAd, Front Porch and Phorm. US ISPs monitoring their customers include Knology,^[6] and Wide Open West, and probably also Embarq. In addition, the UK ISP British Telecom has admitted testing technology from Phorm without their customers' knowledge or consent.^[7]

[edit] Quality of service

Applications such as peer-to-peer (P2P) traffic present increasing problems for broadband service providers. P2P traffic is typically used by applications that do file sharing. This can be files, music and videos. Due to the frequently large size of media files being transferred, P2P drives increasing traffic loads, requiring additional network capacity. Service providers say a minority of users generate large quantities of P2P traffic and degrade performance for the majority of broadband subscribers using applications such as email or Web browsing which use less bandwidth.^[8] Poor network performance increases customer dissatisfaction and leads to a decline in service revenues.

DPI allows the operators to ensure equitable bandwidth to all users by preventing network congestion. Additionally, a higher priority can be allocated to a VoIP or video conferencing call which requires low latency versus web browsing which does not.^[9] This is the approach that service providers use to dynamically allocate bandwidth according to traffic that is passing through their networks.

Other Vendors claim that DPI is ineffective against P2P and that other methods of Bandwidth Management are more effective.^{[citation needed]}

[edit] Tiered services

Mobile and broadband service providers use DPI as a means to implement tiered service plans, to differentiate "walled garden" services from "value added", “all-you-can-eat" and "one-size-fits-all” data services.^[10] By being able to charge for a "walled garden", per application, per service, or "all-you-can-eat" rather than a "one-size-fits-all" package, the operator can tailor his offering to the individual subscriber and increase their Average Revenue Per User (ARPU). A policy is created per user or user group, and the DPI system in turn enforces that policy, allowing the user access to different services and applications.

[edit] Copyright enforcement

ISPs are sometimes requested by copyright owners or required by courts or official policy to help enforce copyrights. In 2006, one of Denmark's largest ISPs, Tele2, was given a court injunction and told it must block its customers from accessing The Pirate Bay, a launching point for Bit Torrent.^[11] Instead of prosecuting file sharers one at a time,^[12] the International Federation of the Phonographic Industry (IFPI) and the big four record labels EMI, Sony BMG, Universal Music and Warner Music have begun suing ISPs like Eircom for not doing enough about protecting their copyrights.^[13] The IFPI wants ISPs to filter traffic to remove illicitly uploaded and downloaded copyrighted material from their network, despite European directive 2000/31/EC clearly stating that ISPs may not be put under a general obligation to monitor the information they transmit and directive 2002/58/EC granting European citizens a right to privacy of communications. The Motion Picture Association of America (MPAA) which enforces movie copyrights, on the other hand has taken the position with the FCC that network neutrality could hurt anti-piracy technology such as Deep Packet Inspection and other forms of filtering.^[14] To protect themselves against lawsuits, court injunctions, and government policies and regulations, ISPs are employing DPI to prevent illegal distribution of copyrighted materials by their subscribers.

[edit] Deep Packet Inspection by governments

In addition to using DPI for the security of their own networks, governments in North America, Europe and Asia use DPI for various purposes such as surveillance and censorship; many of these programs are classified.^[15]

[edit] United States

The NSA, with cooperation from AT&T has used Deep Packet Inspection technology to make internet traffic surveillance, sorting and forwarding more intelligent. The DPI is used to find which packets are carrying e-mail or a Voice over Internet Protocol (VoIP) phone call.^[16] Traffic associated with AT&T’s Common Backbone was "split" between two fibers, dividing the signal so that 50 percent of the signal strength went to each output fiber. One of the output fibers was diverted to a secure room; the other carried communications on to AT&T’s switching equipment. The secure room contained Narus traffic analyzers and logic servers; Narus states that such devices are capable of real-time data collection (recording data for consideration) and capture at 10 gigabits per second. Certain traffic was selected and sent over a dedicated line to a "central location" for analysis. According to Marcus’s affidavit, the diverted traffic "represented all, or substantially all, of AT&T’s peering traffic in the San Francisco Bay area," and thus, "the designers of the ... configuration made no attempt, in terms of location or position of the fiber split, to exclude data sources comprised primarily of domestic data."^[17] Narus's Semantic Traffic Analyzer software which runs on IBM or Dell Linux servers, using DPI technology, sorts through IP traffic at 10Gbit/s to pick out specific messages based on a targeted e-mail address, IP address or, in the case of VOIP, phone number.^[18] President George W. Bush and Attorney General Alberto R. Gonzales have asserted that they believe the president has the authority to order secret intercepts of telephone and e-mail exchanges between people inside the United States and their contacts abroad without obtaining a FISA warrant.^[19]

The Defense Information Systems Agency has developed a sensor platform that uses Deep Packet Inspection.^[20]

[edit] China

The Chinese government uses Deep Packet Inspection to monitor and censor network traffic and content that it claims harmful to Chinese citizens or state interests. This material includes pornography, information on religion, and political dissent.^[21] People within China often find themselves blocked while accessing Web sites containing content related to Taiwanese and Tibetan independence, Falun Gong, the Dalai Lama, the Tiananmen Square protests and massacre of 1989, political parties that oppose that of the ruling Communist party, or a variety of anti-Communist movements.^[22] China also blocks VOIP traffic in and out of their country (though skype seems to work without problem),^[18] as well as visual media sites like YouTube.com and various photography and blogging sites.^[23]

[edit] Iran

The Iranian government purchased a system, reportedly for deep packet inspection, in 2008 from Nokia Siemens Networks (NSN), a joint venture Siemens AG, the German conglomerate, and Nokia Corp., the Finnish cellphone company, according to a report in the Wall Street Journal in June, 2009, quoting NSN spokesperson Ben Roome. According to unnamed experts cited in the article, the system "enables authorities to not only block communication but to monitor it to gather information about individuals, as well as alter it for disinformation purposes."

The system was purchased by the Telecommunication Infrastructure Co., part of the Iranian government's telecom monopoly. According to the Journal, NSN "provided equipment to Iran last year under the internationally recognized concept of 'lawful intercept,' said Mr. Roome. That relates to intercepting data for the purposes of combating terrorism, child pornography, drug trafficking and other criminal activities carried out online, a capability that most if not all telecom companies have, he said. ... The monitoring center that Nokia Siemens Networks sold to Iran was described in a company brochure as allowing 'the monitoring and interception of all types of voice and data communication on all networks.' The joint venture exited the business that included the monitoring equipment, what it called 'intelligence solutions,' at the end of March, by selling it to Perusa Partners Fund 1 LP, a Munich-based investment firm, Mr. Roome said. He said the company determined it was no longer part of its core business."

The NSN system followed on purchases by Iran from Secure Computing Corp. earlier in the decade.^[24]

Questions have been raised about the reporting reliability of the Journal report by David Isenberg, an independent Washington, D.C.-based analyst and Cato Institute Adjunct Scholar, specifically saying that Mr. Roome is denying the quotes attributed to him and that he, Isenberg, had similar complaints with one of the same Journal reporters himself in an earlier story.^[25] NSN has issued the following denial: NSN "has not provided any deep packet inspection, web censorship or Internet filtering capability to Iran."^[26] A concurrent article in The New York Times said the NSN sale had been covered in a "spate of news reports in April [2009], including The Washington Times," and reviewed censorship of the Internet and other media in the country, but did not mention DPI.^[27]

[edit] DPI and net neutrality

People and organizations concerned about privacy or network neutrality find inspection of the content layers of the Internet protocol to be offensive.^[4] "The 'Net was built on open access and non-discrimination of packets!"^[28][who?] Critics^[who?] of network neutrality rules, meanwhile, call them "a solution in search of a problem" and believe that net neutrality rules would reduce incentives to upgrade networks and launch next-generation network services.^[29]

[edit] See also

• Common carrier
• Deep packet capture
• Firewall
• Foreign Intelligence Surveillance Act
• Golden Shield
• Intrusion prevention/detection systems
• Network neutrality
• NSA warrantless surveillance controversy
• Stateful firewall

[edit] References

[edit] External links

• Test Methodology
• Subverting Deep Packet Inspection the Right Way
• What is "Deep Inspection"?
• A collection of essays from industry experts
• What Is Deep Packet Inspection and Why the Controversy