The National Crime Agency (NCA) had suggested that individuals follow the advice on the website in order to help protect themselves against powerful malware such as GOZeus and Cryptolocker, however it became inaccessible shortly after the NCA's announcement on Monday.
Get Safe Online's chief executive Tony Neate said: "We're looking at what we can do to make sure this won't happen again. We're sorry. I've had no sleep for two days."
The site has since quadrupled its capacity and is back up and running properly.
Sign up for CIO Asia eNewsletters.