Here is some information from CSIS site, unable to post link
Immigration and Citizenship Screening
The provision of security advice in immigration and citizenship matters is crucial to countering imported threats to the security of Canada. The screening program serves as a first line of defence against those who attempt to penetrate the country to undermine Canadian security.
Working closely with Citizenship and Immigration Canada (CIC), the Service's Immigration Screening program's primary task is to provide security-related advice to CIC. The objective is to prevent persons who are inadmissible under the Immigration and Refugee Protection Act (IRPA) from entering or gaining status in Canada.
One important change, that has been introduced in the past few years, from a security screening point of view, is the adoption of Front End Screening (FES) for all refugee claimants to Canada. FES is a government initiative to ensure that all refugee claimants arriving in Canada are checked against CSIS and RCMP records before they are sent to the Immigration and Refugee Board. The initiative was implemented to identify and filter potential security and criminal cases from the refugee claimant stream as early as possible in the determination process. Prior to FES, CSIS did not screen refugee claimants.
In addition to its new responsibilities for Front End Screening, the Service, for many years, has had the responsibility for conducting security screening of immigrants and refugees who apply for permanent residence status from both within Canada and outside Canada. CSIS provides advice to the Minister of Citizenship and Immigration related directly to the security inadmissibility criteria contained in the Immigration and Refugee Protection Act. CSIS also provides CIC with security assessments on applicants for Canadian citizenship. CIC forwards all applications for citizenship to CSIS for review. The Service advises if any security concerns relating to a particular application surfaced in the course of its checks, and provides CIC with relevant security advice if such concerns come to light.
The use of information technology has greatly assisted in reducing the time needed to process requests from CIC. In 1996-1997, the Service began to receive its trace requests related to citizenship applications through an Electronic Data Exchange directly from CIC's Case Processing Centre in Sydney, Nova Scotia. Beginning in November 2001, CIC has also made available an input process for all immigration officers in Canada, enabling CIC front-line officers to send data to CSIS electronically, greatly facilitating the front end screening process. Screening requests for immigrants applying to CIC from within Canada are now all conducted electronically between the Service and CIC. Requests related to immigrants applications from outside of Canada traditionally took longer to process since such applications were sent to the Service on hard copy forms and mailed via diplomatic bags. However, electronic exchange systems installed at posts abroad have significantly reduced turnaround times. CSIS is also increasing the number of liaison officers abroad to further improve processing of these applications and reduce existing backlogs.
Over the fiscal year 2003-2004, the Service received some 44,907 requests for Immigration Screening from within Canada (including RDP) and issued 46,183 security clearance assessments. Additionally, the Service received some 24,243 Immigration Screening applications from outside Canada and 4,646 from the United States for a total of 73,796 immigration cases. The median turnaround time was 42 days (through the Electronic Data Exchange Program) for requests from within Canada. Under the Overseas Program, our Security Liaison Officers were consulted on 4,814 cases.
Citizenship Screening is conducted on the basis of threats to Canada's security as set out in s.19 of Citizenship Act. Over the past years, 203,356 citizenship requests were received from Citizenship and Immigration Canada.