Yet the unrelenting distributed denial-of-service (DDoS) attacks aimed at U.S. banks continue to cause headaches. In the last week of January, for example, more than a third of requests to HSBC's consumer banking site failed, according to Internet measurement firm Keynote. Almost 30 percent of requests to Citizens Bank and Regions Bank were likewise dropped.
While the financial industry, along with DDoS mitigation firms, continue to work to blunt the attacks, security experts worry that similar combinations of data floods, along with targeted packets aimed at tying up application resources, could wreak havoc among more sensitive operational environments.
"The spotlight is starting to shift to critical infrastructure," Bryan Sartin, director of Verizon's RISK team, said in an interview last month. "It is not necessarily the banks, but these other areas where we need to look at reinforcing right now, because what if the tide of these attacks shift there? This could be a demonstration that that next step is entirely possible. That's vulnerability."
Denial-of-service (DoS) attacks used to be the hacker's attack of last resort -- a digital club lacking in subtlety. Yet, over time, cybercriminals have added sophistication and a great deal more heft to the attack. Today's DoS attacks consume massive bandwidth, averaging 1 Gbps and frequently topping 50 Gbps, while concealing more subtle attacks aimed at tying up application servers, according to Internet security firms.
Criminals have frequently used the threat of DoS attacks -- often followed by the real thing -- to extort money from vulnerable businesses, including critical-infrastructure operators. More than half of all such organizations have suffered a large DoS attack, according to a report published by McAfee in 2010. Most companies do not talk about such incidents, but manufacturers have lost production because of viruses or worms causing instabilities in their networks, or DoS attacks shutting down systems, said Joel Langill, an industrial control system (ICS) security specialist.
"In control systems, a denial-of-service attack is a success," he says. "If you can cause a DoS on control systems, you actually accomplish your mission."
In 2011, for example, systems at brewery SABMiller had to be shut down to eradicate the Conficker worm, costing the firm £7.2 million. While that attack consisted of the mindless spread of Conficker compromising sensitive systems, similar techniques could be used to get inside an operator's network and cause problems.
[Data is not readily available on the attacks hitting financial institutions, but defenders dealing with the incidents say that the attacks are effective and costly. See Monitoring Bank DDoS Attacks Tough Task For Third Parties.]
Critical-infrastructure companies have become vulnerable to attack because they have integrated the Internet into their businesses to save money, says Toralv Dirro, EMEA security strategist for McAfee, a subsidiary of Intel.
"We have seen companies, in the course of saving money, utilizing the Internet more and more, and ... using the internal network more and more to enable access to their control systems from other points of the network, instead of keeping it separate," he says.
While the controllers may be cordoned off from the Internet, compromising a system in the corporate office can often allow an attacker to gain access to operational systems, consultant Langill says.
"Go through the fence, go past the industrial wall, and those systems do not have the same protections in place," he says. Because of the long life cycle of industrial systems, the systems are often 10 to 15 years old -- a time when security, and the threat, was very different. "You can DoS a controller by sending a single packet to it," Langill added.
To solve the security issues, infrastructure operators need to audit their own security, and not just from external threats. Most attacks against infrastructure are aimed at compromising an internal computer and then using insider-like access to move into the control environment, he says.
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