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DoS attacks getting scarier

OAKLAND, Calf.--Windows users and Internet routing equipment are the

latest pawns of malicious intruders intent on launching denial of service

attacks online, an expert from Carnegie Mellon's CERT Coordination Center

warned network operators here Monday.

Attackers have begun favoring particular chunks of Internet address space

that are more likely to contain Windows machines than others, said Kevin

Houle, a researcher with the government-funded center, speaking to

approximately 600 engineers and network administrators at a meeting of the

North American Network Operators' Group (NANOG). "If I'm an intruder and

I want to install my tools on Windows machines, its very easy to find

subsections of the network to search," said Houle.

So-called distributed denial of service (DDoS) attacks rely on an

attacker's ability to install malicous agents on a large number of

computers, and use them to simultaneously flood a victim with overwhelming

traffic. The shift from Unix machines to Windows computers began in late

2000, said Houle, and has grown noticeably in recent months.

The mechanisms for controlling large numbers of compromised boxes have

also changed, said Houle, becoming vastly more sophisticated since DDoS

attacks began in 1999. Attackers increasingly use IRC -- the Internet's

chat room systems -- to direct attacks, sometimes using domain name

records as a kind of dead drop for directing their agents to a particular

IRC server.

More disturbing to network operators, attackers have taking over the

machines that route and direct the flow of Internet traffic, to use them

as weapons, Houle said.

"What we see are routers with default and weak passwords being targeted,"

Houle said. After cracking a router, attackers can use it to launch

straightforward denial of service attacks against an Internet site.

Because routers can generate enough traffic to impede an end host, while

standing up well to a similar counterattack, it's become a valued platform

for cyber vandals engaged in online skirmishes in the mostly-juvenile

computer underground.

"If I'm an intruder and I want to be well protected against people DoSing

me, a router is somewhat better than an end host," said Houle.

The development is foreboding, Houle said, because of the possibility that

attackers could begin targeting the protocols that link routers to one

another, potentially leading to disruptions in the Internet's fundamental

infrastructure. "This is stuff that's being talked about, not just within

the security community, but also the intruder community," said Houle.

Generally, speakers at NANOG agreed that conditions haven't improved much

since February 2000, when a fifteen-year-old Canadian boy used distributed

denial of service tools to flood sites like eBay, and Yahoo! with

traffic, knocking them offline.

In fact, attackers are now able to marshal so many machines in a DDoS

attack, that they seldom bother to tamper with the packets to disguise

their source. "If you have 200 compromised machines, it doesn't matter if

the source addresses are spoofed or not," said Jason Slagle, network

administrator at Toledo Internet Access, an Ohio ISP. By Kevin Poulsen

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