The phrase "deterioration of security" is correct and usable in written English.
You can use it to refer to a decline in safety or protection, such as when discussing national security or the security of personal possessions. For example, "With the deterioration of security in the region, it's become harder for citizens to feel safe in their own homes."
The casualty in a province known as relatively secure was a reminder of the deterioration of security across Afghanistan.
The deterioration of security within rebel-controlled areas leaves journalists susceptible to future kidnappings.
With our attention focused on Iraq, we run the risk of overlooking the alarming deterioration of security in Afghanistan.
The incident comes amid a deterioration of security in and around the Iraqi capital after months of relative calm.
Moreover, Mrs. Clinton said, the deterioration of security in nuclear-armed Pakistan "poses a mortal threat to the security and safety of our country and the world".
Instead, the events at the U.S. Embassy seem to reflect the general deterioration of security around the country, especially with regard to diplomatic missions.
She claimed she had sacked the three ministers "to prevent further deterioration of the security situation".
By the same token, the current status quo in Afghanistan — the slow but steady deterioration of the security situation and growing influence of the Taliban — is unacceptable.
In the last few years we have seen a dramatic deterioration of our security, with a more assertive Russia and turmoil across north Africa and the Middle East.
In a 35-minute speech to Parliament, Mr. Barak did not find any new words to address the radical deterioration of Israeli security, diplomacy and politics that has taken place since the lawmakers recessed in July.
He said a response from election authorities was necessary to "protect political stability and to prevent a deterioration of the security situation that could lead to a return of violence".
