A Computer Security Incident Response Team (CSIRT) is a service organization that is responsible for receiving, reviewing, and responding to computer security incident reports and activity. Their services are usually performed for a defined constituency that could be a parent entity such as a corporation, governmental, or educational organization; a region or country; a research network; or a paying client.
A CSIRT can be a formalized team or an ad hoc team. A formalized team performs incident response work as its major job function. An ad hoc team is called together during an ongoing computer security incident or to respond to an incident when the need arises.