The DNS amplification vulnerability, which was exploited to the fullest in the attacks on Spamhaus, return incoming requests to a DNS server with as much as 100 times as much data. When the attackers have faked the source address for those incoming requests, the responses can overwhelm the victims’ servers — and possibly spill over and clog the Net.
What is the aftermath of the massive Distributed Denial of Service attacks recently on the anti-spam Spamhaus organization? As the largest such attack in history, the digital assault on Spamhaus slowed network performance in some regions of Europe and elsewhere, raised alarms about whether the Net could reach a breaking point, and has become a historic event that could mark a turning point.
According to reports in The New York Times and elsewhere, a key figure in the attacks appears to be Sven Olaf Kamphuis, who is associated with CyberBunker, the Dutch hosting facility where the attacks originated. After the Europe-based Spamhaus put CyberBunker on its spam blacklist, because of what Spamhaus said were substantial streams of spam e-mails coming from that hosting facility, the DDoS attacks began.
Kamphuis maintains a Facebook page, in which he champions hosting services such as CyberBunker for providing open Net access, and he rails against Spamhaus for acting like an arbitrary authority.
Like ‘The Mafia’
CyberBunker has said it will allow customers to host anything except “child porn and anything related to terrorism.” Spamhaus is backed by a variety of e-mail services, and experts have testified in court that many e-mail services would be rendered useless by the flood of spam if not for the organization’s efforts.
But this massive wave of DDoS attacks — in which Web servers are overwhelmed by a flood of bogus traffic — broke some boundaries, according to Garth Bruen, an adviser to the consumer-oriented Digital Citizens Alliance. Bruen told USA Today that the attacks from CyberBunker were like “the kind of things we saw the mafia do to take control of neighborhoods 50 years ago.”
He added that what was particularly “troubling” is that CyberBunker is a commercial ISP “working with shadowy figures in undisclosed locations.”
Open DNS Resolvers
The attacks have highlighted some ongoing weaknesses in the Internet’s infrastructure . Key among these are open Domain Name System resolvers, which allow attackers to engage in so-called DNS amplification. One of the weaknesses of open resolvers is that they do not authenticate a sender’s address before replying.
This vulnerability, which was exploited to the fullest in the attacks on Spamhaus, return incoming requests to a DNS server with as much as 100 times as much data . When the attackers have faked the source address for those incoming requests, the responses can overwhelm the victims’ servers — and possibly spill over and clog other parts of the Net.
DNS servers are critical to the Internet as they translate alphanumeric-based Web addresses like “www.google.com” into the numeric IP addresses that computers can understand.
The Spamhaus attacks reportedly utilized more than 30,000 unique DNS resolvers. There are efforts, such as the Open DNS Resolver Project, to convince DNS administrators to implement source address validation, among other actions, to eliminate open DNS resolvers as a Net-wide weakness.
There are also calls for IT departments and individual PC owners to make a greater effort to scan their computers for signs of malware that could be hijacking their machines into becoming part of a botnet. Additionally, the Electronic Frontier Foundation and others have offered tips to small businesses on how to cope with DDoS attacks, if their sites become one of the direct or indirect targets.
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