A group of hackers known as the Lizard Squad recently targeted the National Crime Agency (NCA) website, bringing it down for a few hours.
The attack is claimed to be "revenge" after the NCA arrested a number of teenagers with connections to the group.
Lizard Squad used a Distributed Denial of Service (DDoS) attack to bring the website down, but the NCA was quick to claim it had not been hacked.
"The NCA website is an attractive target. Attacks on it are a fact of life. DDoS is a blunt form of attack, which takes volume and not skill. It isn't a security breach, and it doesn't affect our operational capability. At worst it is a temporary inconvenience to users of our website," a statement said.
"We have a duty to balance the value of keeping our website accessible with the cost of doing so, especially in the face of a threat which can scale up endlessly.
"The measures we have in place at present mean that our site is generally up and running again within 30 minutes, though occasionally it can take longer. We think that is proportionate," it added.
Around 9am yesterday, the NCA website went offline and Lizard Squad claimed responsibility with a Twitter message containing the site's address and "#stressedout."
Although access to the website was restored around two hours later, it did briefly go offline again around an hour later.
The attack came after August 28th, when six individuals were arrested for using a tool offered by Lizard Squad.