The National Cyber Security Centre (NCSC) has been working with the defence industry to reduce the risks of cyber attacks.
Cyber security experts have been working alongside the Ministry of Defence (MOD) and the defence sector to identify vulnerabilities and find new ways to protect top-secret information.
In the last 12 months, the NCSC says it has dealt with 658 cyber attacks on the UK.
Ciaran Martin, the centre's chief executive, said a "significant number of incidents continue to come from hostile nation states".
He said Russia, China, Iran and North Korea "continue to pose strategic national security threats to the UK".
However, Mr Martin did not give details about the "operational successes" made by the NCSC.
The centre is working closely with the UK defence industry to help protect some of the nation's most-secret information.
The defence sector currently takes up around 10% of the NCSC's workload, from providing advice on cyber security risks to the UK's Continuous At Sea Nuclear Deterrent to the new F-35B fighter jets.
The Government is investing in greater cyber defences and the NCSC is working alongside the MOD to create new methods of information sharing.
There is also a focus on protecting the public sector.
The report by the NCSC revealed that it had handled more than one million cases of suspected credit card fraud.
Speaking at a conference, Mr Martin said: "Some attackers are still doing the same things over-and-over again, and too often, they are getting through.
"But there are things you and I can do, as individuals, and organisational leaders can do, to get ahead of the problem.
"All of us can use sensible, practical measures like better passwords, two-factor authentication and backups."
The centre, which is part of the Government Communications Headquarters (GCHQ), was set up as part of a £1.9 billion cyber security strategy.