Police in the North have said a poster with details of three serving officers was placed on a bus shelter in Co Derry.
An investigation has been launched into the incident in Chapel Road in Dungiven on Thursday.
It follows a major data breach last month where the details of around 10,000 officers and staff were mistakenly released online.
Assistant Chief Constable Chris Todd said: “We have contacted those involved to make them aware and recognise the impact this may have on them and their families.
“The safety and welfare of all our officers and staff remains our priority and additional security and reassurance patrols have already been implemented across Northern Ireland as part of our organisational response.
“We have commenced an investigation into this matter and I appeal to anyone with any information relating to this incident to contact police on 101.
“We are particularly keen to hear from anyone who was travelling through Dungiven last night and who has any dash cam footage.”
Details of around 10,000 PSNI officers and staff including the surname and first initial of every employee, their rank or grade, where they are based and the unit they work in were mistakenly released online in response to a Freedom of Information request.
ThePSNIhas confirmed the list is in the hands of dissident republicans, who continue to target officers.
The admission came after redacted information from the breach was posted on the wall of a library in west Belfast near a Sinn Féin office.
Just earlier this year Detective Chief Inspector John Caldwell was shot a number of times at a leisure facility in Co Tyrone.
Police officers and their representative organisations have spoken out in recent weeks over concern for their safety.
A number of other data breaches have since come to light, including the loss of a police officer’s laptop and notebook which contained details of 42 officers and members of staff after the items fell from a moving vehicle.
An independent review of the circumstances of the data breach is to be carried out, led by City of London Police Assistant Commissioner Peter O’Doherty.
It will look at process and actions leading to thebreachand if any organisational, governance or management issues allowed it to happen.
Last month a man appeared in court in Co Antrim charged with two terror offences relating to the data breach.