Distributed denial-of-service attacks get bigger and combine application-layer exploits requiring defenders to be more agile.
n the past, attackers using distributed denial-of-service (DDoS) attacks to take down Web sites or network servers typically adopted one of two tactics: Flooding the site with a deluge of data or overwhelming an application server with seemingly valid requests.
Companies concerned about denial-of-service attacks have generally focused more on mitigating data floods, also known as volumetric or infrastructure attacks. Yet, increasingly attackers are using a hybrid approach, using multiple vectors to attack. The attacks that hit financial firms in September and October, for example, often used a massive flood of data packets that would overwhelm a victim’s network connection, while a much smaller subset of traffic would target vulnerable applications functions, consuming server resources.
“It is almost like sending a whole squadron of tanks and then have an assault team that can go in and be mores stealthy in taking out their targets,” says Carlos Morales, vice president of global sales engineering and operations for network protection firm Arbor Networks. “It broke the model that people had for stopping these things.”
The one-two punch is potent. Many financial firms thought they had the defenses in place to defeat such attacks but had problems staying accessible during the onslaught. Companies prepared to handle application-layer attacks or smaller volumetric attacks could not handle the 20Gbps or more that saturated their Internet connection. Even a gateway that can keep up with 10Gbps connection speed cannot deal with twice as much–or more–traffic sent to the same server.
A recent report from network-security firm Prolexic found that the average attack bandwidth had increased to nearly 5Gbps, with 20Gbps attacks quite common. In a year, the average volume of attacks had doubled, the firm found.
“The late Senator Ted Stevens got mocked for saying that the Internet is a ‘series of tubes,'” says Matthew Prince, CEO of Cloudflare, a content-delivery and network-security firm. “But the Internet is a series of tubes, and you can only fit so much through it.”
Companies must start creating a multi-layered approach to stopping distributed denial-of-service attacks, according to mitigation experts. The greatest amount of attack volume should be stopped inside a provider’s network, away from the company’s links to the Internet. Trying to over-provision your network for the worst case scenario will likely not work and will be very expensive to boot.
“Even if you are a large bank in the U.S., you are doing less than 10Gbps of traffic across all the properties of your network combined,” says Cloudflare’s Prince. “If you have to over-provision that by 10x, that is wasting a lot of resources.”
By using a service provider to filter out most of the spurious traffic at the edge of the Internet, companies can pay attention to the data that actually enters their network. Collecting information on the traffic can help a company to better develop defenses for future attacks as well, even if a company does not have the resources to identify attacks in real time.
Yet, faster detection and more agile response can mean the difference between successful defenses and downtime.
“Seeing an impact and understanding that there is an attack happening is not necessarily going to happen at the same time,” says Neal Quinn, chief operating officer for attack-mitigation service Prolexic.
For many companies, the threat of attacks is not over, but rather, just beginning. The most recent attacks did not start with the financial industry; other industries have been hit by similar attacks for almost the last year. Companies should not expect it to end there either. The holiday season tends to be a popular time for attackers to attempt to extort money from retailers by threatening denial-of-service attacks.
“It is traditionally a very busy time of year for these attacks,” Prolexic’s Quinn says. “If anything, organizations should make themselves more aware of how well they can handle these attacks.”