AT&T says a distributed denial of service attack Aug. 15 impacted some of its DNS servers and disrupted Internet service for some of its customers.
AT&T said the company was hit with a distributed denial of service attack (DDoS) Aug. 15 that disrupted Internet
service for some of its customers.
The attack, which reportedly lasted
, affected domain name system servers belonging to the
"Due to a distributed denial
of service attack
attempting to flood our Domain Name System servers in two
locations, some AT&T business customers experienced intermittent
disruptions in service on Wednesday," a spokesperson told eWEEK
network and security teams quickly worked to mitigate the impact and service is
currently running normally."
"We apologize for any inconvenience to our
customers," the spokesperson added.
The company did not offer information about whether
it is boosting its DDoS defenses in light of the attack.
"DDoS attack mitigation is a very complex and dynamic
cat and mouse problem," said Jeff Lyon, president of security company
Black Lotus. "Those who design attack vectors for the specific purpose of
circumventing defense measures are equally, if not more, intelligent than the
security engineers implementing solutions to the problem."
Several years ago, DNS reflection attacks and TCP SYN floods
would have been the most difficult attack vectors, he explained. The major
challenge today, however, is with complex attacks at the application layer (Layer
7) that deplete resources of the server itself by mimicking real users in a way
that is very difficult to detect. In recent months, he added, attackers have
begun targeting Websites that rely on SSL by exploiting a Web server's ability
to handle large amounts of HTTPS sessions.
"Increasingly, we are seeing that DDoS
attacks against high-profile targets are intelligent, determined and persistent,"
said Neil Roiter, director of research at Corero Network Security.
"It is therefore essential the DDoS response plan defines
when and how additional mitigation resources are engaged and surveillance
tightened," he said.
A brute-force or flooding DDoS attack is relatively easy to
identify but it requires high performance and sophisticated real-time analysis
to recognize and block attack traffic while simultaneously allowing legitimate
traffic to pass, Roiter said. Detecting application layer attacks requires
a thorough understanding of the typical behaviors and actions of bonafide
customers or employees accessing the applications being protected.
"In much the same way that credit card fraud detection may
be automated, on-premises DDoS defense systems establish legitimate usage
profiles in order to identify suspicious traffic and respond accordingly," he
In addition, Roiter said organizations should make it a priority to protect their DNS servers.
"The Internet Domain Name System (DNS) is a distributed
naming system that enables us to access the Internet by using recognizable and
easy to remember names such as www.google.com
rather than numeric IP addresses (e.g.
192.168.0.1) on which network infrastructure relies to route messages from one
computer to another," he said.
"Since DNS is distributed, many organizations use and
maintain their own DNS servers to make their systems visible on the Internet. These
servers are often targeted by DDoS attacks. If the attacker can disrupt DNS
operations, all of the victims' services may disappear from the Internet,
causing the desired Denial of Service effect."