John Buchanan, a sergeant at Police Scotland, was given the job after conducting a high-level review of the SNP leader's safety.
However, the move was criticised by Labour chief whip Lewis Macdonald, who accused Salmond of treating the Government and the police as "wholly-owned subsidiaries of the SNP".
Buchanan, an officer with experience of dealing with firearms incidents, was seconded to the Government earlier this year to conduct his review.
The exercise focused on arrangements in Bute House and the First Minister's home in Aberdeenshire.
It is also believed to have touched on security protocol when Salmond is on walkabout.
Following the review, Buchanan is now based in the First Minister's private office as a "security liaison officer".
His job is to scope out potential threats and plan for events attended by Salmond, such as deciding on the best entrance for the First Minister to use. He was also part of the Government entourage that visited China in November.
However, a police spokesman said the role did not amount to a bodyguard.
Buchanan served in the old Lothian and Borders force before it made way for Police Scotland.
He was also a "project officer" on the Chemical Biological Radiological and Nuclear (CBRN) response programme. Business documents describe him as a "close protection trainer", as well as a director and co-shareholder of a dormant company, Vigilax.
It is believed Salmond's high profile, as well as the prominence of the independence referendum, triggered the security rethink.
Although his security has been beefed up, Salmond does not receive the same service as those afforded to Prime Ministers, selected Cabinet ministers and ambassadors.
The Metropolitan Police provides "personal protection" to these individuals, which entails officers constantly travelling with their subjects.
A Government source said politicians such as Salmond were less anxious about violence than they were about getting splattered by paint or a custard pie.
Jack McConnell, Salmond's predecessor as First Minister, did not have his own security adviser.
Buchanan's role is believed to be open-ended and not time-limited.
Labour chief whip Macdonald said: "Alex Salmond's approval ratings may be going down, but his opinion of his own importance only ever goes up.
"He is the first minister in a devolved government in a democratic country, accountable to an elected parliament, not a supreme leader whose importance is measured by the size of his entourage.
"Maybe when he remembers that, he will stop treating the Scottish Government and Police Scotland as wholly-owned subsidiaries of the SNP."
A Police spokesperson said: "Following a review of security surrounding the First Minister for Scotland, a security liaison officer from Police Scotland has been seconded to the office of the First Minister.
"The role of this officer is to provide advice and guidance on physical and protective security measures, including visits and events, in relation to the First Minister."
A Scottish Government spokesperson said: "We do not comment on security issues."