Defence minister Andrew Murrison has said Britain has contingency plans in place if hit by a "sustained cyber attack".
Mr Murrison rejected claims that the Government is not doing enough to protect cyber security, adding that £650 million would be invested over the next four years in the national cyber security strategy programme.
He said: "The UK Armed Forces and the equipment and assets they use are amongst the world's most modern and advanced, so of course information technology plays a vital role in their operation.
"Far from being complacent, the MoD takes the protection of our systems extremely seriously and has a range of contingency plans in place to defend against increasingly sophisticated attacks although, for reasons of national security, we would not discuss these in detail.
"Government funding to tackle this threat underlines the importance we attach to these issues."
His comments came after MPs warned the armed forces are now so dependent on information technology that their ability to operate could be "fatally compromised" by a sustained cyber attack.
The Commons Defence Committee said the cyber threat to UK security had the ability to evolve at "almost unimaginable speed" and questioned whether the Government had the capacity to deal with it.
It called on ministers to take a more hands-on approach to ensure proper contingency plans were in place.
The committee said: "The evidence we received leaves us concerned that with the armed forces now so dependent on information and communications technology, should such systems suffer a sustained cyber attack, their ability to operate could be fatally compromised.
"Given the inevitable inadequacy of the measures available to protect against a constantly changing and evolving threat ... it is not enough for the armed forces to do their best to prevent an effective attack.
"In its response to this report the Government should set out details of the contingency plans it has in place should such an attack occur. If it has none, it should say so - and urgently create some."