Complex event processing (CEP) is a new technology. It can be applied to extracting and analyzing information from any kind of distributed message-based system. It is developed from the Rapide concepts of (1) causal event modeling, (2) event patterns and pattern matching, and (3) event pattern maps and constraints. Complex event processing can be applied to a wide variety of Enterprise monitoring and management problems, from low level network management to high level enterprise intelligence gathering.

Applications of Complex Event Processing:

• Instant Insight  - hierarchical event viewing applied to the Enterprise IT layer. (coming soon)
  • Analysing business processes (paper in pdf format)
• Network Level Monitoring and Management (Powerpoint presentation)
• Cyber Security: Network Intrusion Detection
• Enterprise Monitoring and Management (coming soon)
• Modeling and Simulation of Collaborative Business Processes
• Business Policy Monitoring. (coming soon)
• Analysis and Debugging of Distributed Systems (coming soon)

Presentations:

• “Complex Event Processing: An Essential Technology for Instant Insight into the Operation of Enterprise Information Systems,” lecture at the Stanford University Computer Systems Laborary EE380 Colloquium series. Video of the lecture (duration: 60 minutes).

Publications:

• Complex Event Processing in Distributed Systems. David C. Luckham and Brian Frasca, Stanford University Technical Report CSL-TR-98-754, March 1998, 28 pages.Abstract: Complex event processing is a new technology for extracting information from distributed message-based systems. This technology allows users of a system to specify the information that is of interest to them. It can be low level network processing data or high level enterprise management intelligence, depending upon the role and viewpoint of individual users. And it can be changed from moment to moment while the target system is in operation. This paper presents an overview of Complex Event Processing applied to a particular example of a distributed message-based system, a fabrication process management system. The concepts of causal event histories, event patterns, event filtering, and event aggregation are introduced and their application to the process management system is illustrated by simple examples. This paper gives the reader an overview of Complex Event Processing concepts and illustrates how they can be applied using the Rapide toolset to one specific kind of system.
   
• Event Mining with Event Processing Networks. Louis Perrochon and Walter Mann and Stephane Kasriel and David C. Luckham, The Third Pacific-Asia Conference on Knowledge Discovery and Data Mining. April 26-28, 1999. Beijing, China, 5 pages.Abstract: Event Mining discovers and delivers information and knowledge in a real-time stream of data, or events. We show that the process of delivering knowledge by searching patterns in data and subsequent abstraction of found patterns can be applied in real-time to a complex, asynchronous system. Our event processing engine consists of a network of event processing agents (EPAs) running in parallel that interact using a dedicated event processing infrastructure. The agents can be configured at run-time using a formal pattern language. The underlying infrastructure (1) provides an abstract communication mechanism and thus allows dynamic reconfiguration of the communication topology between agents at run-time and (2) provides transparent, location-independent access to all data. These features allow dynamic allocation of EPAs to different threads and processes on different machines at run time.
   
• eJava - Extending Java with Causality. Alexandre Santoro and Walter Mann and Neel Madhav and David Luckham, Proceedings of the 10th International Conference on Software Engineering and Knowledge Engineering, June 1998, 10 pages.Abstract: Programming languages like Java provide designers with a variety of classes that simplify the process of program development. Some of these classes allow one to easily build multithreaded programs. Though useful, especially in the creation of reactive systems, multithreaded programs present challenging problems such as race conditions and synchronization issues. Validating these programs against a specification is not trivial since Java does not clearly indicate thread interaction. These problems can be solved by modifying Java so that it produces computations, collections of events with both causal and temporal ordering relations defined for them. Specifically, the causal ordering is ideal for identifying thread interaction. This paper presents eJava, an extension to Java that is both event based and causally aware, and shows how it simplifies the process of understanding and debugging multithreaded programs.
   
• Event-Based Execution Architectures for Dynamic Software Systems. James Vera, Louis Perrochon, David C. Luckham.
  Proceedings of the First Working IFIP Conf. on Software Architecture. 1999. San Antonio, Texas.Abstract: Distributed systems’ runtime behavior can be difficult to understand. Concurrent, distributed activity make notions of global state difficult to grasp. We focus on the runtime structure of a system, its execution architecture, and propose representing its evolution as a partially ordered set of predefined architectural event types. This representation allows a system’s topology to be visualized, analyzed and con-strained. The use of a predefined event types allows the execution architectures of different systems to be readily compared.
   
• Using Context-Based Correlation in Network Operations and Management. Louis Perrochon (work in progress, mail author for newest version)Abstract: Network operation consists to a large degree of reaction to activities happening in the network. Better knowledge of the network at any time allows more appropriate reactions. On the example of intrusion detection, we show how context-based correlation of such activities can provide a more detailed view of the network in shorter time. We first present how we model context and then describe the architecture of the Stanford University CEP context-based correlator. Correlation is specified as event patterns in a declarative language that allows us to specify what needs to be detected, instead of specifying how it should be detected. CEP introduces the concept of causal context to intrusion detection. The correlator is able to process events on-line, as they are generated and it can be reconfigured at dynamically. We then show how it increases detection rate, reduce false alarms, and detect large-scale attack patterns at an early stage.

Weldon, who is currently being investigated by the FBI over alleged corruption during his time in office, visited Libya in March to discuss a possible military deal, according to a letter describing the trip from Weldon to Defense Solutions CEO Timothy Ringgold. In May, Weldon, together with Ringgold and another company representative, traveled to Moscow to discuss working with Russia's weapons-export agency on arms sales to the Middle East.

Both trips were part of the company's effort to tap into the growing -- and often legally murky -- market for selling weapons from former Eastern Bloc countries to the Middle East and Afghanistan.

Ex-Rep. Curt Weldon, R-Penn., is helping broker deals between Russian weapons suppliers and the Iraqi and Libyan governments through his company, Defense Solutions.
Photo: H. Rumph Jr/AP

The Russians want to sell weapons to Iraq directly, but "must go slow on Iraq because of political reasons" and want to work with an "intermediary" like Defense Solutions, CEO Ringgold subsequently wrote to colleagues. "They have not spoken with any American company that can offer the quid pro quo that we can or that has the connections in Russia that we have," he boasted.

A few years ago, an American company proposing to sell weapons to Libya might have triggered a congressional hearing. So, too, would have a proposal to conduct arms deals with Russia, which the United States has accused of selling high-tech weapons to Syria and Iran.

However, U.S. government efforts to rapidly equip countries like Afghanistan and Iraq -- which have largely Soviet-origin weapons -- have created legal ambiguities and loopholes in export controls that didn't exist in years past and given rise to a new class of arms trade middlemen. So, even though both Libya and the Russian arms export agency are on official U.S. blacklists, government officials and analysts involved in weapons sales say the rules have become unclear as the push to equip allies in the global war on terror has blazed new but uncertain legal ground.

Eagerly stepping into that virgin territory is Defense Solutions, a Pennsylvania-based company that is carving out a small but lucrative niche in a new international arms bazaar. The firm boasts as its advisors a number of influential Washington insiders, such as retired General Barry McCaffrey, the former White House drug czar.

Helping the firm make key connections is Curt Weldon, a former Republican congressman from Pennsylvania at the center of an FBI investigation into alleged conflicts of interest during his time in office. Weldon, now a key executive at Defense Solutions, is working with the company to set up these weapons deals.

Defense Solutions has also proposed refurbishing Libya's BTR-60 armored personnel carriers, according to a sales proposal seen by Wired.com. Defense Solutions denies drafting a sales proposal to Libya.

It's an unusual, if not an entirely unexpected chapter for Weldon, whose time in office included frequent trips to Russia. As an influential member of the House Armed Services Committee, Weldon pushed for multibillion-dollar defense programs, like ballistic missile defense, and earned a reputation as a foreign policy gadfly, boasting of his contacts with officials in nations labeled by the administration as "rogue states" such as Libya and North Korea. Weldon's wild claims about a 9/11 cover-up and his sensationalist book warning of an Iranian terror plot, sometimes earned him official scorn and public ridicule, but it was accusations that he steered contracts to Eastern European businesses linked to his daughter's lobbying firm that drew the government's attention.

Weldon was voted out of office in 2006 just weeks after the FBI raided his daughter's home, and that of one of her associates.

Weldon did not respond to e-mails and phone requests to be interviewed or comment for this article. But in a 2006 interview, before the FBI probe was public, Weldon spoke enthusiastically about setting up a "front company" to work with the Russian arms agency, Rosoboronexport. Weldon hoped this company could sell weapons to the Middle East, and other regions, particularly to countries where the U.S. has strained relations. He claimed the director of Rosoboronexport approached him to work with "an American company that would act as a front for weapons these nations want to buy."

Weldon called the proposal an "unbelievable offer."

The administration, he acknowledged at the time, did not welcome the idea of an American company selling Russian weapons to potentially unfriendly countries. But two years later, Weldon, now a private citizen and chief strategic officer for Defense Solutions, appears to be working on precisely that sort of deal. And whether illegal or not, Defense Solutions' business represents a new phenomenon in the international arms trade business.

In years past arms brokers -- firms or individuals who serve as middlemen to facilitate weapons sales between countries -- were largely the stuff of spy thrillers. Unlike traditional American defense companies, like Lockheed Martin or Boeing, which typically sell weapons directly to NATO countries or other governments regarded as friendly to the United States, brokers are often small outfits run by people with sometimes questionable experience and reputations they will sell to anyone. One of the most infamous arms brokers, a Russian named Viktor Bout, is charged by the United States, United Nations, Interpol and others of funneling arms to terrorists and rebels around the world. He was recently arrested in Thailand. The United States is requesting his extradition on charges of supplying arms to a terrorist organization.

Two Marines lower the trim vane on the front of an Iraqi BMP-1 mechanized infantry combat vehicle that was captured during Operation Desert Storm. The American defense consulting firm Defense Solutions has proposed refurbishing Libya's aging fleet of BMP-1s. Defense Solutions denies drafting a sales proposal to Libya.

But ironically, Iraq has fueled a new market for these professional middlemen; the United States is funneling billions of dollars into modernizing Iraq's army so that the country's government can fend for itself after coalition troops withdraw. And Iraq's largely Soviet-equipped military is a natural market for Eastern European countries brimming with old or out-of-date equipment they would like to unload. The middlemen, in these cases, serve a key role by allowing the U.S. government to do business with an American company, which in turn buys equipment from Eastern Bloc countries in deals worth hundreds of millions of dollars, much of it financed with U.S. taxpayer dollars.

One of Defense Solutions' sales -- a deal to sell Hungarian-owed T-72 tanks to Iraq in 2005 -- was typical of these new foreign military sales. But on the more questionable side is the company's plans to work with Rosoboronexport, which is barred from doing business with the U.S. government, and Libya, which is still on the State Department's arms embargo list.

The Eastern European-Middle East arms-brokering business, while in some cases sanctioned by the U.S. government, has run into problems, including outright corruption and quality. Defense contractor Dale Stoffel, the president of Wye Oak Technology, and another American were gunned down in Iraq in December 2004 after Stoffel alleged that the Iraqi Ministry of Defense was involved in a kickback scheme. Like Defense Solutions, the company Stoffel worked for was refurbishing the Iraq's army Eastern Bloc equipment.

Another problem is quality. Weapons from the former Soviet Bloc, which the U.S. military euphemistically calls "nonstandard equipment," have been flagged as substandard, acknowledges Brigadier General Charles Luckey, who is in charge of security assistance at Multi-National Security Transition Command-Iraq. In an interview from Iraq, Brigadier General Luckey said: "One of the frustrating things about buying nonstandard [weapons], is that I'm the guy who has to deal with the fact that some broker I've never heard of allowed weapons to get to Iraq before they were inspected."

Defense Solutions is carving a new niche in the arms trade, selling Soviet-made weapons to Middle Eastern countries like Afghanistan and Iraq. Defense Solutions sold Hungarian-owed T-72 tanks to Iraq in 2005.

In one high-profile case, Iraqi officials alleged that a corrupt firm sold them $400 million in shoddy helicopters from Poland. More recently, a company led by a 21-year-old and a former masseur was offered a U.S. government contract worth nearly $300 million to sell ammunition to Afghanistan. The ammunition turned out to be outdated and of dubious origin and several people connected with the company have been indicted. A congressional investigation concluded that the company, which was on a State Department watch list, was able to take advantage of regulatory loopholes by using middlemen.

For those concerned about illicit arms trade, this new wave of weapons deals is rife with the potential for corruption and abuse, but for companies eager to pursue markets once regarded as dubious, it represents a lucrative business opportunity. The problem in these cases, according to those familiar with arms sales, is that it's no longer clear what's legal and what's not.

Rachel Stohl, an expert on international arms trade and a senior analyst at Center for Defense Information, says that in many ways, the rush to equip Iraq has led the United States to throw caution to the wind. She points to a report by the Government Accountability Office last year that found that some 190,000 weapons sold to Iraq have gone missing. "I think the reality is we won't know, until way after the fact, about all of these irregularities with the Iraq weapons provision program," she said. "We were providing them all these assault rifles that have gone missing. Why? They were not following the standard procedures that were in place."

But Iraq and Afghanistan aren't the only markets available to arms brokers like Defense Solutions. The gradual normalization of relations with Libya opens another door into a quasi-legal area of sales.

Like Iraq, Libya has a substantial arsenal of Soviet-origin military weapons, offering a potential market for brokers working with Russia and other former Soviet states. But even when there's not an outright ban, sales to the Middle East are often fraught with controversy, particularly to countries like Libya, which was under international sanction for more than a decade. Even as sanctions against it have been lifted, European companies proposing to sell arms to Libya have faced steep criticism, particularly since the country is still ruled by dictator Muammar Gaddafi, who took power in a military coup in 1969.

While the United States lifted Libya's "state sponsor of terrorism" designation in 2006, other restrictions, such as on the sale of arms, remain in place. A State Department spokesperson confirmed that exports of "lethal munitions" to Libya, such as tanks or related equipment, are still banned, although sales of nonlethal equipment are now allowed on a case-by-case basis.

In late March, Weldon traveled to Libya for a weeklong trip at the invitation of the Gaddafi Foundation, a group run by the son of Libya's leader, and the chairman of Libya's foreign affairs committee, according to the report he sent to Defense Solutions (.pdf), a copy of which was obtained by Wired.com. The trip reports states: "Agreement reached for Weldon to quickly return to Libya for meetings with son [of Libyan leader Gaddafi] Morti regarding defense and security cooperation."

A document dated April 16, just two weeks after Weldon's trip, outlines Defense Solutions' proposal to Libya to refurbish the country's fleet of armored vehicles, including its T-72 tanks, BMP-1 infantry fighting vehicles, and BTR-60 armored personnel carriers. A copy of the sales proposal, also provided to Wired.com, is on Defense Solutions' letterhead, appears to bear the signature of company CEO Timothy Ringgold, and is addressed to Libya's defense procurement council. "Defense Solutions is committed to delivering a full end-to-end solution to its clients," the proposal states. "Besides refurbishing these vehicles, we are capable of providing a full logistics support package, including a two year supply of spare parts, maintenance and repair services, and operator, maintenance, and repair training."

In an interview with Wired.com, Ringgold admitted that he's interested in doing business in Libya and confirms receiving Weldon's trip report from Libya, but denies drafting or signing an arms-sale proposal. "I've never made such a document to Libya," Ringgold insisted, after being read the proposal, and told that his signature is on it.

In addition to the Libyan arms-deal document, Wired.com has also reviewed copies of e-mails from Ringgold discussing the Libyan deal.

While Ringgold denies proposing an arms sale to Libya, he is open about speaking with Rosoboronexport, which has been on a U.S. government sanctions list since 2006, after the Russian state agency allegedly violated the Iran and Syria Nonproliferation Act. An April e-mail provided to Wired.com describes Ringgold, Weldon and Stephan Minikes, a senior advisor to Defense Solutions and a former ambassador, meeting with Rosoboronexport. The conversations included a number of potential deals, including supplying Mi-17 helicopters to Afghanistan and spare parts for Iraq's infantry fighting vehicles. Ringgold wrote to colleagues following the visit, describing the meetings as a "spectacular success," saying the Russian agency "has the ability to undercut all cost proposals from brokers."

Ringgold confirmed those discussions and said that his company has sought to do business with Rosoboronexport. Asked whether Ringgold considers his dealings with Russia to be legal, he argued that U.S. companies could work with Rosoboronexport on a "case-by-case" basis. "The particular purpose of the meeting we had -- and I want to be crystal clear -- was in response to a U.S. government requirement," he said.

A number of officials at the State Department and in the Pentagon, when contacted for this article, could not say whether working with Rosoboronexport is legal or not. A Pentagon spokeswoman said she was familiar with the issue, but deferred the question to the State Department. When asked about Rosoboronexport's status on the blacklist, John Herzberg, a State Department spokesman replied: "What's on there is on there."

Asked whether, given the ban, there was any way a company could legally work with Rosoboronexport, as Ringgold suggested, Herzberg provided an equivocal answer. "At the stage of the process we're at, I'm unable to give you an answer," he said. "You can try elsewhere in government, and maybe they'll be braver than me."

In an interview from Iraq, General Luckey conceded it was a murky area, but said, "My understanding is they are currently on our no-go list."

The confusion over debarred parties has even led the U.S. government into its own legal tangles, according to Jim McAleese, a Washington attorney who specializes in government contracting and foreign military sales. Because the Russian government violated U.S. nonproliferation laws, even NASA had to go to Congress to ensure it could work with Russia on Soyuz flights to the international space station. "What I'm warning you about is, don't be surprised by the confusion," McAleese said. "There are a whole bunch of different statutes that were adopted piecemeal and were never intended to be reconciled."

But it's the very ambiguity of the law that troubles those who monitor export control. "It's highly unusual to do anything with the Russians, particularly Rosoboronexport," said Scott Jones, director of Export Control Programs at the Center for International Trade and Security at the University of Georgia.

Legal or not, reputable American companies simply don't want to work with banned entities, Jones said, for fear of risking their reputations and business. "Even if it's not an outright prohibition, most companies don't want to put themselves in a liability situation that has really bad PR … and they stay away from it," Jones said. "But if that's your business, pimping out arms from the U.S. or Russia, that's the way it works, and you push as much as possible."

Finding any U.S. defense company working with the Russian government at this point would be "remarkable," Jones added.

In the meantime, the future for Weldon is unclear. The FBI investigation continues and Weldon's former chief of staff recently pleaded guilty to a conspiracy charge and is cooperating with the government, notes Melanie Sloan, the executive director of Citizens for Responsibility and Ethics in Washington, which filed a complaint against Weldon in 2004. Sloan speculated that Weldon may be charged with "honest service fraud" for misusing his office for personal gain. "It's an easier standard than bribery," she said. "I wouldn't be surprised [if he's charged] with bribery, but I think it will be honest services fraud."

Ringgold insists that he and Weldon are on the right side of the law. "Everything we do is in strict compliance with international and U.S. law and we operate only in the best interests of the U.S. government," he said. "I didn't serve 30 years in the United States Army to throw that away on a whim."

Asked if Weldon is still working for the company, Ringgold replied: "Absolutely, proudly so."

• Conduct regular security assessments of Web-based applications. The universities first need to determine how many Web-based applications they have and then make provisions to regularly update their lists of applications.  They then need to develop and implement procedures for regularly conducting security reviews of their critical Web-based applications.

• Develop a university-wide policy and associated procedures for updating Web servers, which are computers that host Web-based applications. Software vulnerabilities are constantly being discovered and publicized, and the universities need to develop or enhance: (1) procedures for identifying vulnerabilities relevant to their Web servers, (2) a timeline for reacting to notifications of newly discovered Web server vulnerabilities, and (3) a process for determining whether to apply a software update, establish another control to address the Web server vulnerability, or accept the risk of not updating the software.
• Ensure that security is built into the process for developing Web-based applications. According to ASU, UA, and NAU officials, none of them have university-wide security standards for developing applications. According to an IT best practice, building security into the development process is more cost-effective and secure than applying it afterwards.
• Provide training to application developers so that they are aware of common Web-based application vulnerabilities and methodologies that can be used to avoid them. None of the universities have a training program that is mandatory for all users and geared toward an individual's role within the university.
  

Nashua, N.H.'s downtown network may never launch: The local paper says, c'mon, already. The network was to span a 1.2-mi stretch of the main street and use donations. Deadlines have come and gone for a year.

Covad may launch San Carlos, Calif., test network: The company know for wired installations as the last-man-standing among competitive DSL and other digital line providers nationwide, is looking for city access to build a square mile test area. This is the latest wrinkle in trying to get Wireless Silicon Valley underway after the consortium was unable to raise funds, and lead-partner Azulstar stepped back or was replaced.

Lexington, Kent., may relaunch shuttered network: The city bought SkyTel's network assets for $10 over a year ago--10 dollars, not 10 plus any zeroes--and the city may partner with the University of Kentucky to build a public-safety network. The university would manage the network. It's unclear from the article if any public access would be included.

Blogger: Dan Blum

One of our service directors likes to quote William Gibson: “The future is here, it’s just unevenly distributed.”

At Microsoft’s Server and Tools Business (STB) Analyst and Tech Ed conferences last week, I saw a vendor and a user community living in the past, present and future with many unevenly distributed capabilities.

In a session on identity management strategy, for example, Microsoft discussed a variety of initiatives. These range from Card Space (futuristic implementation of user-centric Information Card specifications) to ADFS (present day enterprise federation support, though unfortunately lacking full SAML capabilities) to self-service password reset exposed through Office (decidedly backward-looking as this functionality has been available from many vendors through browsers for many years).

In another session on rights management and SharePoint, Microsoft highlighted the opportunity to configure SharePoint libraries to automatically apply Active Directory Rights Management Services protections on downloaded documents. Digital rights management (DRM) is controversial and no strong guarantor of confidentiality. Nonetheless, it is a  way to put futuristic self-protecting wrappers on content so as to prevent its accidental leakage or misuse by honest, cooperative users. Because it’s not something that can resist certain types of malicious attackers, many security professionals look down their noses at rights management. Nonetheless, preventing accidental misuse of enterprise information is a big part of the space. It was clear from the number of people in the room asking intelligent questions suggesting realistic expectations that customers see potential value for this technology.

Finally, I was impressed by a presentation on IPSec, PKI and NAP by a Brazilian university IT manager named Rodrigo Imaginario. Starting three years ago, the university combined its student and administrative networks into a single network. Yet servers running ERP and containing administrative content (such as grading information) need to be protected from a subset of students going through their hacking stage. Imaginario implemented a logical security zoning overlay on top of the network using IPSEC in Windows. In the restricted zone, servers only accept connections from Kerberos-authenticated IPSEC clients in the administrative domain. Today, the authentication is being upgraded to use PKI for secure, all campus wireless networking. Imaginario indicated the university took the Windows IPSEC route approach because no additional software had to be purchased. Configuration was difficult, he said, but will get easier with Windows Server 2008. This sounds like an idea whose time has come.

Blogger: Dan Blum

One of our service directors likes to quote William Gibson: ???The future is here, it???s just unevenly distributed.???

At Microsoft???s Server and Tools Business (STB) Analyst and Tech Ed conferences last week, I saw a vendor and a user community living in the past, present and future with many unevenly distributed capabilities.

In a session on identity management strategy, for example, Microsoft discussed a variety of initiatives. These range from Card Space (futuristic implementation of user-centric Information Card specifications) to ADFS (present day enterprise federation support, though unfortunately lacking full SAML capabilities) to self-service password reset exposed through Office (decidedly backward-looking as this functionality has been available from many vendors through browsers for many years).

In another session on rights management and SharePoint, Microsoft highlighted the opportunity to configure SharePoint libraries to automatically apply Active Directory Rights Management Services protections on downloaded documents. Digital rights management (DRM) is controversial and no strong guarantor of confidentiality. Nonetheless, it is a  way to put futuristic self-protecting wrappers on content so as to prevent its accidental leakage or misuse by honest, cooperative users. Because it???s not something that can resist certain types of malicious attackers, many security professionals look down their noses at rights management. Nonetheless, preventing accidental misuse of enterprise information is a big part of the space. It was clear from the number of people in the room asking intelligent questions suggesting realistic expectations that customers see potential value for this technology.

Finally, I was impressed by a presentation on IPSec, PKI and NAP by a Brazilian university IT manager named Rodrigo Imaginario. Starting three years ago, the university combined its student and administrative networks into a single network. Yet servers running ERP and containing administrative content (such as grading information) need to be protected from a subset of students going through their hacking stage. Imaginario implemented a logical security zoning overlay on top of the network using IPSEC in Windows. In the restricted zone, servers only accept connections from Kerberos-authenticated IPSEC clients in the administrative domain. Today, the authentication is being upgraded to use PKI for secure, all campus wireless networking. Imaginario indicated the university took the Windows IPSEC route approach because no additional software had to be purchased. Configuration was difficult, he said, but will get easier with Windows Server 2008. This sounds like an idea whose time has come.

The new compression technique, called variable bitrate compression produces different size packets of data for different sounds.

That happens because the sampling rate is kept high for long complex sounds like "ow", but cut down for simple consonants like "c". This variable method saves on bandwidth, while maintaining sound quality.

VoIP streams are encrypted to prevent eavesdropping. However, a team from John Hopkins University in Baltimore, Maryland, US, has shown that simply measuring the size of packets without decoding them can identify whole words and phrases with a high rate of accuracy.

The technique isn't good enough to decode entire conversations, but it's pretty impressive.