The Ministry of Defence has warned of an increasingly blase attitude towards data security amongst what it terms the "Facebook generation".
In a new report, the MoD says that it has noted that young armed forces recruits do not take data security seriously enough.
Young recruits were used to the "rapid and often uninhibited exchange of information", the report says.
But "this behaviour must be tempered by common sense and sound judgment ... and the particular concerns of MoD work", report author Sir Edmund Burton noted.
Burton was asked to investigate the theft of a MoD laptop with the records of 600,000 recruits from a Royal Navy recruiter's car last January.
The car had been parked overnight in the Edgbaston district of Birmingham.
Investigators found that it was one of four such laptops - out of a total of just 55 - to have been stolen since 2004, and all of them were taken from parked cars.
Burton was highly critical of the ministry in its report saying it had lost its Cold War discipline for data security and there was "little awareness" of its importance among staff.
As a result a major security incident had been "inevitable".
"During the Cold War, awareness of real security was ingrained in individuals and organisations", his report said.
"Audit, inspection, and compliance regimes were rigorously underpinned by codes of discipline."
"These well-developed processes and procedures have not been translated, effectively into the information age."
"Generally, there is little awareness of the current, real, threat to information, and hence to the department's ability to deliver and support operational capability."
"Consequently, there can be little assurance that information is being effectively protected", the report says.