Information technology consulting (also called IT consulting, computer consultancy, business and technology services, computing consultancy, technology consulting, and IT advisory) as a field of activity focuses on advising organizations on how best to use information technology (IT) in achieving their business objectives.

The IT consulting industry can be viewed as a four-tier system:

Professional services firms that maintain large professional workforces and command high bill rates.
Staffing firms, which place technologists with businesses on a temporary basis, typically in response to employee absences, temporary skill shortages, and technical projects.
Independent consultants, who are self-employed or who function as employees of staffing firms (for US tax purposes, employed on Form W-2), or as independent contractors in their own right (for US tax purposes, on "1099").

Information Technology security consultants.There are different reasons why consultants are called in:

To gain external, objective advice and recommendations
To gain access to the consultants' specialized expertise
Temporary help during a one-time project where the hiring of a permanent employee(s) is not required or necessary
To outsource all or part of the IT services from a specific company.