"Anonymous" DDoS Activity

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US-CERT has received information from multiple sources about coordinated distributed denial-of-service (DDoS) attacks with targets that included U.S. government agency and entertainment industry websites. The loosely affiliated, collective "Anonymous" allegedly promoted the attacks in response to the shutdown of the file-hosting site MegaUpload and in protest of proposed U.S. legislation concerning online trafficking in copyrighted intellectual property and counterfeit goods (Stop Online Piracy Act, or SOPA, and Preventing Real Online Threats to Economic Creativity and Theft of Intellectual Property Act, or PIPA).

US-CERT has evidence of two types of DDoS attacks: one using HTTP GET requests and another using a simple UDP flood.

Low Orbit Ion Cannon (LOIC) is a DoS-attack tool associated with previous Anonymous activity. US-CERT has reviewed at least two implementations of LOIC. One variant is written in JavaScript and designed to be used from a web browser. An attacker can access this variant of LOIC on a website and select targets, specify an optional message, throttle attack traffic, and monitor attack progress. A binary variant of LOIC includes the ability to join a botnet to allow nodes to be controlled via IRC or RSS command channels (the "HiveMind" feature).

The following is a sample of LOIC traffic recorded in a web server log:

"GET /?id=1327014400570&msg=We%20Are%20Legion! HTTP/1.1" 200 99406 "hxxp://" "Mozilla/5.0 (Windows NT 6.1; WOW64; rv:9.0.1) Gecko/20100101 Firefox/9.0.1"

The following sites have been identified in HTTP referrer headers of suspected LOIC traffic. This list may not be complete. Please do not visit any of the links because they may still host functioning LOIC or other malicious code.



The HTTP requests contained an "id" value based on UNIX time and a user-defined "msg" value, for example

GET /?id=1327014189930&msg=%C2%A1%C2%A1NO%20NOS%20GUSTA%20LA%20

Other "msg" examples include

msg=Stop%20S.O.P.A%20:)%20%E2%99%AB%E2%99%AB HTTP/1.1" 200 99406 ""

The "msg" field can be arbitrarily set by the attacker.

Prior to January 20, 2012, US-CERT observed additional DDoS attacks that consisted of UDP packets on ports 25 and 80. The packets contained a message followed by variable amounts of padding, for example

66:6c:6f:6f:64:00:00:00:00:00:00:00:00:00 | flood.........

Target selection, timing, and other attack activity is often coordinated through social media sites or online forums.

US-CERT is continuing research efforts and will provide additional data as it becomes available.


A remote, unauthenticated attacker could execute arbitrary code, cause a denial of service, or gain unauthorized access to your files or system.


A number of mitigation strategies are available for dealing with DDoS attacks, depending on the type of attack and the target network infrastructure. In general, the best practice defense for mitigating DDoS attacks involves advanced preparation:

  • Develop a checklist or standard operating procedure (SOP) to follow in the event of a DDoS attack. One critical item in a checklist or SOP is having contact information for your ISP and hosting providers. Identify who should be contacted during a DDoS, what processes should be followed, what information is needed, and what actions will be taken during the attack with each entity.
  • The ISP or hosting provider may provide DDoS mitigation services. Ensure that your staff is aware of the provisions of your service level agreement (SLA).
  • Maintain contact information for firewall teams, IDS teams, and network teams, and ensure that it is current and readily available.
  • Identify critical services that must be maintained during an attack, as well as their priority. Services should be prioritized beforehand to identify what resources can be turned off or blocked as needed to limit the effects of the attack. Also, ensure that critical systems have sufficient capacity to withstand a DDoS attack.
  • Have current network diagrams, IT infrastructure details, and asset inventories. They will help you determine actions and priorities as the attack progresses.
  • Understand your current environment, and have a baseline of the daily volume, type, and performance of network traffic. Doing so will allow staff to better identify the type of attack, the point of attack, and the attack vector used. Also, identify any existing bottlenecks and remediation actions if required.
  • Harden the configuration settings of your network, operating systems, and applications by disabling services and applications not required for a system to perform its intended function. 
  • Implement a bogon block list at the network boundary.
  • Employ service screening on edge routers wherever possible in order to decrease the load on stateful security devices such as firewalls.
  • Separate or compartmentalize critical services:
    • Separate public and private services.
    • Separate intranet, extranet, and internet services.
    • Create single-purpose servers for each service such as HTTP, FTP, and DNS.
  • Review the US-CERT Cyber Security Tip Understanding Denial-of-Service Attacks.



January 24, 2012: Initial release|January 26, 2012: Updated|April 23, 2012: Updated

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