The Internet鈥檚 organic structure explains why it鈥檚 so resistant to random failures, but researchers now say those same features make it vulnerable to cyberattacks. The findings could help security experts strengthen weak links in the Net鈥檚 chain.p. THE LATEST STUDY, published in Thursday鈥檚 issue of the journal Nature, builds on earlier studies of the researchers, Reka Albert, Hawoong Jeong and Albert-Laszlo Barabasi.p. They found that samples of the World Wide Web didn鈥檛 have a random structure: Instead, the connections exhibited a hierarchy similar to that found in naturally occurring networks such as trees and living cells, with a small proportion of highly connected nodes branching off to a large number of less connected nodes. The structure was the same at different scales, meaning that the results could be extended to the Web as a whole, they said.p. This 鈥渟cale-free鈥� pattern is reflected in the structure of the Internet 鈥� that is, the global network of routers and lines knitting computers together 鈥攁s well as in the connections between Web pages sitting on those computers.p. In the new study, the trio focused on the implications for the Internet鈥檚 survivability in the face of failure. Turning again to their 鈥渟mall-world鈥� samples, they found thatthe Internet, the Web and other scale-free networks could stand up to even unrealistically high rates of random failures.p. 鈥淓ven when as many as 5 percent of the nodes fail, the communication network between the remaining nodes in the network is unaffected,鈥� they reported.p. That鈥檚 because in most cases, random failure 鈥榮ay, the breakdown of an Internet data router 鈥攚ill affect nodes with little connectivity. The flow of Net traffic can simply take another, no less convenient route. In contrast, the performance of a randomly connected network, also known as an exponential network, degrades steadily as failures increase.p. This explains why the Internet chugs right along even though pieces of the network frequently break down.p. "The system evolved into this stage in which it鈥檚 completely tolerant against errors, and it鈥檚 not only because of redundancy," Barabasi said in a telephone interview from Romania, where he鈥檚 on sabbatical. 鈥淚t鈥檚 much more than redundancy.鈥漰. But the researchers say there鈥檚 a flip side: Although the structure is particularly well-suited to tolerate random errors, it鈥檚 also particularly vulnerable to deliberate attack, they said. If just 1 percent of the most highly connected Internet routers or Web sites are incapacitated, the network鈥檚 average performance would be cut in half, said Yuhai Tu of IBM鈥檚 T.J. Watson Research Center.p. 鈥淲ith only 4 percent of its most important nodes destroyed, the Internet loses its integrity, becoming fragmented into small disconnected domains,鈥� he wrote in a commentary published in Nature.p. This vulnerability represented the 鈥淎chilles鈥� heel鈥� of the Internet, Tu said. An attack on the key Internet access points would be far more serious than an attack on the biggest Web sites, Barabasi said. 鈥淭hen there鈥檚 no Internet, there鈥檚 no e-mail, there鈥檚 no Web, because you can鈥檛 get from A to B,鈥� he said.p. Internet security experts who reviewed the research said it meshed with their own real-world experience, although they cautioned that other factors helped guard against cyberattacks.p. The Internet traffic network has some intersections so key that 鈥渋f you take down this limited number of points, you could take down a great deal of connectivity,鈥� said Jim Jones, director for technical operations for response services at Global Integrity Corp., a Virginia-based computer security firm.p. However, Jones noted that the 91吃瓜 study was based on a 鈥淭he Internet is not static, and the snapshot they took of it may not match the backup connections that may kick in. 鈥� There are redundancies that wouldn鈥檛 necessarily show up,鈥� he said.p. A potential attacker would have to have a detailed knowledge of how the Net works, how to take down key Internet locations that are heavily protected precisely because they鈥檙e so essential, and how to cut off the backup avenues.p. Another expert took issue with the 91吃瓜 researchers鈥� claim that the Internet was inherently vulnerable to attack. 鈥淎ctually, these problems aren鈥檛 inherent at all 鈥� and we can eliminate them,鈥� said David A. Fisher, simulation at the CERT Coordination Center in Pittsburgh. The center is among the nation鈥檚 pre-eminent As the Internet becomes more distributed and less hierarchical, the number of potential targets should decline, he said. 鈥淭here are only a few of noticeable, but it鈥檚 not because of a weakness,鈥� he said.p. Jones said the research validates what鈥檚 known about Internet security a little more rigorously, 鈥渁nd certainly gives us some better directions鈥� on how to address the Net鈥檚 natural vulnerabilities.p. 鈥淭he structure of the Internet is a product more of economics than design,鈥� he noted. To cite an exaggerated example, it鈥檚 cheaper to link less connected nodes to a bigger-bandwidth backbone than to install fiber-optic lines and heavy-duty routers in every household.p. 鈥淚f we were to design (the Internet) as an exponential network, we would have decent survivability to random error and incredible survivability to directed attack 鈥� but it would be incomprehensible to do that because of the cost,鈥� he said.p. Nevertheless, making the Internet more uniformly connected might be a goal to shoot for, he said. To cite a real-world example, Jones compared the current Internet to the Napster file-swapping site, while the more dispersed Gnutella service has more of 鈥淲ith Gnutella, I have no one point to focus on,鈥� Jones said.p. Mark Rasch, a former federal prosecutor who is now Global Integrity鈥檚 vice president for cyber law, said an exponential approach would also make it 鈥渕uch more difficult to regulate Internet content, because it grows organically.鈥漰. Rasch said another way to beef up the Internet鈥檚 survivability in the face of attack would be to 鈥渂uild off a second Internet,鈥� such as the high-bandwidth Internet2 infrastructure currently in development.p. But Fisher said redundancy alone would not protect the Internet from deliberate attack.p. 鈥淲e鈥檙e concerned not so much with failures in the traditional sense, but with intelligent adversaries who are trying to cause failures,鈥� he said.p. "It turns out that redudnacy doesn鈥檛 help at all. What helps is redundancy coupled with diversity.p. If network administrators use the same setup for all their primary and backup systems, that simply leads to a situation in which 鈥渙ne attack fits everybody,鈥� he said. In the long run, Fisher said, the best way to fend off mass attacks against any network is to eliminate the single points of failure, wherever they exist.p. p. p. p. p. Wednesday, July 26, 2000
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