A computer hacking organisation known for its anti-US sentiments successfully broke into at least two US Army web servers, InformationWeek reports.
On 29 May, President Barack Obama announced that the nation's computer network would now be defended as a national strategic asset. The White House has also announced that a cyber security coordinator will be appointed to the national security staff.
According to the InformationWeek report, the hackers were based in Turkey and go by the name 'm0sted'.
The hackers managed to penetrate servers at the McAlester ammunition plant in Oklahoma and the US Army Corps of Engineers transatlantic centre in Winchester, Virginia.
The breach, which occurred on 26 January 2009, redirected users of the site to a web page protesting against climate change. It is not clear whether or not the hackers managed to obtain any sensitive information.
The same hackers also broke into US Army Corps of Engineers servers in September 2007.
Investigators believe that the hackers used a technique known as SQL injection to exploit vulnerabilities in Microsoft's SQL server database to gain entry.
The US Department of Defense and other investigators are currently probing the breaches, which have not been publicly disclosed.