It is responsible for the installation, maintenance and operation of communications and information systems for the command, control and administration of the Defence Forces, and the facilitation of accurate, real-time sharing of intelligence between the Army, Naval Service and Air Corps branches at home and overseas.

[1] The CIS Corps collar flash features the angel Gabriel, the messenger of God, behind a signal shield and the caption "Cór Comharthaíochta".

[6][7] CIS is responsible for cyber security within the Defence Forces, and maintains a capability in that area for the purpose of protecting its own networks and users domestic and foreign.

[9] In July 2015, leaked email correspondence from Hacking Team – a private Italian spying and eavesdropping software company – reportedly showed members of the Irish CIS Corps in discussions with the company to purchase intrusion and surveillance "solutions" for the lawful interception of online communications, such as monitoring incoming and outgoing emails, browsing activity, Skype calls, remotely switching on webcams and microphones and remotely taking control of devices.

[10][11] A Defence Forces spokesperson said that for operational security reasons, it could not comment on specific elements of the activities of the CIS Corps, but confirmed that no goods or services were purchased from the company in question.