The Royal Navy web site has been the victim of a hacking attack and is currently offline.
Security firm Sophos said that the attack was carried out by a Romanian hacker known as 'Tinkode' who has been connected to attacks on sites run by Nasa and the US Army.
The cause of the attack is believed to be an SQL code injection vulnerability. Such methods have been used in the past to trigger major security breaches.
Graham Cluley, senior technology consultant at Sophos, said that the site has been compromised, but that the actual damage is far less than it could have been.
"We can all be thankful that Tinkode's activities appear to be have been more mischievous than dangerous," he said in a blog post.
"If someone with more malice in mind had hacked the site they could have used it to post malicious links on the Navy's JackSpeak blog, or embedded a Trojan horse into the site's main page."
Currently the site displays a window notifying visitors that the site is undergoing "essential maintenance".
The attack comes just days after the UK and other EU member nations tested systems against a simulated attack.
The drill attempted to recreate a co-ordinated effort to cripple network infrastructure throughout Europe, and test international cyber defence systems and agencies.
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