US defence firm Lockheed Martin says it has come under a significant cyber-attack, which took place last week.

美国防御公司洛克希德马丁称在上周遭受一次严重的网络攻击。

Few details were available, but Lockheed said its security team had detected the threat quickly and ensured that none of its programmes had been compromised.

The Pentagon said it is working to establish the extent of the breach¹.

Lockheed makes fighter jets, warships² and multi-billion dollar weapons systems sold worldwide.

Lt Col April Cunningham, speaking for the US defence department, said the impact on the Pentagon was "minimal³ and we don't expect any adverse⁴ effect（副作用） ".

Lockheed Martin said in a statement that it detected the attack on 21 May "almost immediately" and took counter-measures.

As a result, the company said, "our systems remain secure; no customer, program or employee personal data has been compromised".

But they are still working to restore employee access several days after the attack took place.

Lockheed Martin is the world's biggest aerospace⁵（航空宇宙） company and makes F-16, F-22 and F-35 fighter jets as well as warships.