Gardaí say they are implementing "heightened security measures" after a cyber attack on their computer systems.

An Garda Síochána said a lengthy shutdown of some systems inside the force sparked by the discovery of the security threat ended today.

However, an investigation is continuing into the identity of the external source behind the attempted hack.

Gardaí revealed last week that a new strain of malware had been found on their systems.

They stressed that no data was compromised and that its main database, PULSE, and the Garda website were not affected.

"Working with security experts the threat was identified and an appropriate solution was implemented across all Garda ICT systems," a spokesman at Garda headquarters said.

"An Garda Síochána can confirm that normal service to Garda systems was restored today.

"As a precaution, heightened security measures have been put in place."

All users inside the force were denied access to certain systems for four days after the discovery of the security threat.

"Any security risks to the Garda ICT systems are treated with the highest importance and standard security protocols are implemented," the spokesman added.

The Garda Computer Crime Unit is continuing its investigation into the incident.

The malware involved was referred to as "zero day", meaning it was not previously known.