Dark Reading is part of the Informa Tech Division of Informa PLC

This site is operated by a business or businesses owned by Informa PLC and all copyright resides with them.Informa PLC's registered office is 5 Howick Place, London SW1P 1WG. Registered in England and Wales. Number 8860726.

Risk

1/22/2014
08:32 AM
50%
50%

No Easy Solution To Stop Amplification Attacks

Denial-of-service attacks powered by NTP amplification interrupted online-gaming services over the past month, renewing efforts to find solutions to the vulnerabilities

A series of attacks against online-gaming services has raised awareness of the ability of certain Internet protocols to be used as a vector for denial-of-service attacks.

In late December and continuing into January, a group of Internet vandals with an apparent vendetta against a single gamer took down online gaming services using an simple amplification attack. By requesting a large list of previous requesters from a vulnerable network time protocol (NTP) server and substituting the target's IP address as the source of the request, the attackers amplified the volume of the attack by a factor of more than 5,500, says Liam O Murchu, manager of security response for Symantec's North American operations.

"So you can send just one short command to the NTP service, and the service will send a list of all computers that have attached to that server to the victim, and that is where you get the amplification," he says. "But the problem with these sorts of attacks is that it is not the victim that has to patch their service -- it is the middleman who is running the outdated service that needs to upgrade."

Security experts have kicked off an initiative to raise awareness of the owners of misconfigured servers running the network time protocol (NTP) to update their systems following a series of attacks by a group of Internet vandals against online-gaming services. The Open NTP project, for example, allows the general public to scan their NTP servers to see whether they allow the monlist command, which the attackers abused to amplify their attacks.

Yet the problem is not restricted to just NTP. Domain name service (DNS) servers that allow anyone to use them, known as open resolvers, are more commonly abused in amplification attacks. In March 2013, such an attack created a record-breaking amount of traffic to inundate anti-spam service Spamhaus.

[What attacks are most likely against cloud computing environments? Here's a look -- and some advice. See How Cybercriminals Attack The Cloud.]

In fact, any protocol that asymmetrically responds to a small request with a larger response could be used to create a distributed denial-of-service attack. While the capabilities that are abused to produce amplification can be sought out, most exist for a good reason, and so it is difficult to triage abusable services until they are actually targeted, says Shawn Marck, CEO of Black Lotus, a denial-of-service mitigation provider.

"It wasn't a vulnerability until someone exploited it -- it was a feature," he says. "But it boils down to any protocol that allows you to make a small request and elicit a large response allows amplification -- unless it is TCP."

Internet communications based on the transmission control protocol (TCP) have a built-in security check: The communication has to be acknowledged by the original sender, essentially making source-address spoofing impossible. Some services that rely on the fire-and-forget communications protocol, known as the user datagram protocol (UDP), first establish a session using TCP and then revert to a stream of communications using UDP. Online gaming and Internet telephony commonly use this technique, Marck says.

Defending against amplification attacks is fairly straightforward, says John Graham-Cumming, a programmer with CloudFlare, a provider of Web security and DDoS mitigation services. NTP attacks can be simply filtered out at the edge of the network before they get to the target. Amplification attacks based on DNS are more difficult, however, since companies want valid DNS queries to arrive at their destination.

"The larger problem with DNS amplification for someone like CloudFlare is that we have to be able to receive DNS packets," he says. "For DNS, it is the nature of our business -- we have to be able to receive unsolicited DNS requests."

By focusing efforts on filtering out DNS responses, the problem become quite tractable, Graham-Cumming says.

For the Internet at large, however, the problem of amplification is not one that is easily solved. Two approaches have emerged: patching each service vulnerable to amplification and requiring service providers to filter out requests from their networks that contain a spoofed source address. While the more general solution would be for Internet service providers to block outgoing packets that contain source addresses outside of their networks, the capability would add costs to their operations, and most ISPs are already running lean, Graham-Cumming says.

It's a matter of incentives, he adds. While spoofing and DNS amplification do not typically impact the Internet service provider, the cost of the solution does. Such external costs to the company, like a company polluting a river, often need government intervention to provide the incentive to do right, Graham-Cumming says.

"It is not a problem for you -- it is a problem for the Internet as a whole, just like polluting a river is not a problem for the polluter but for everyone downstream," he says. "But I think for the network providers, it is probably better for them to do this on their own, rather than having the government come in."

Have a comment on this story? Please click "Add Your Comment" below. If you'd like to contact Dark Reading's editors directly, send us a message. Veteran technology journalist of more than 20 years. Former research engineer. Written for more than two dozen publications, including CNET News.com, Dark Reading, MIT's Technology Review, Popular Science, and Wired News. Five awards for journalism, including Best Deadline ... View Full Bio

Comment  | 
Print  | 
More Insights
Comments
Newest First  |  Oldest First  |  Threaded View
News
Inside the Ransomware Campaigns Targeting Exchange Servers
Kelly Sheridan, Staff Editor, Dark Reading,  4/2/2021
Commentary
Beyond MITRE ATT&CK: The Case for a New Cyber Kill Chain
Rik Turner, Principal Analyst, Infrastructure Solutions, Omdia,  3/30/2021
Register for Dark Reading Newsletters
White Papers
Video
Cartoon
Current Issue
2021 Top Enterprise IT Trends
We've identified the key trends that are poised to impact the IT landscape in 2021. Find out why they're important and how they will affect you today!
Flash Poll
How Enterprises are Developing Secure Applications
How Enterprises are Developing Secure Applications
Recent breaches of third-party apps are driving many organizations to think harder about the security of their off-the-shelf software as they continue to move left in secure software development practices.
Twitter Feed
Dark Reading - Bug Report
Bug Report
Enterprise Vulnerabilities
From DHS/US-CERT's National Vulnerability Database
CVE-2021-30481
PUBLISHED: 2021-04-10
Valve Steam through 2021-04-10, when a Source engine game is installed, allows remote authenticated users to execute arbitrary code because of a buffer overflow that occurs for a Steam invite after one click.
CVE-2021-20020
PUBLISHED: 2021-04-10
A command execution vulnerability in SonicWall GMS 9.3 allows a remote unauthenticated attacker to locally escalate privilege to root.
CVE-2021-30480
PUBLISHED: 2021-04-09
Zoom Chat through 2021-04-09 on Windows and macOS allows certain remote authenticated attackers to execute arbitrary code without user interaction. An attacker must be within the same organization, or an external party who has been accepted as a contact. NOTE: this is specific to the Zoom Chat softw...
CVE-2021-21194
PUBLISHED: 2021-04-09
Use after free in screen sharing in Google Chrome prior to 89.0.4389.114 allowed a remote attacker to potentially exploit heap corruption via a crafted HTML page.
CVE-2021-21195
PUBLISHED: 2021-04-09
Use after free in V8 in Google Chrome prior to 89.0.4389.114 allowed a remote attacker to potentially exploit heap corruption via a crafted HTML page.