Each applicant for a Canadian Immigrant Visa, aged 18 or over, is required to prove that he or she has no criminal record. Police clearance certificates or certificates of non-criminal activity, as they are sometimes referred to, must be obtained from the country of current residence and from each country in which the applicant has resided for more than 6 months since his or her 18th
Police clearance certificates are considered valid for a period of 6 months and they usually can be obtained through law enforcement offices or other government agencies. In extenuating
circumstances Canadian visa offices will waive the requirement to submit police clearance certificates. The background/security check is conducted by Canadian security agencies, independently from the immigration authorities, with and/or without a cooperation of proper agencies and authorities in all countries you have resided for 6 months or more.
This tasks is to find out if you are or were at any time involved in any criminal activity, organized crime, espionage, terrorism, war crimes, crimes against humanity or any other activity that may pose a threat to the security of Canada and Canadians and if you are or were a part of or working for any government or organization involved in war crimes, human rights abuse and crimes against humanity.
Depending on your nationality, background and countries you have resided in this process may take from few months to well over a year to conclude. The procedure, sources and conclusions are strictly classified. Immigration authorities are only getting a "positive" or "negative" result.The CSIS background check for applicants of Canadian citizenship is more comprehensive and involves targeting and monitoring past and present activities of suspected individuals in accordance with the CSIS Act and the CSIS Mandate.
Please note that there is a clear distinction between the police clearance certificate, which the applicant is required to obtain, and the background clearance, in which the applicant for the most part is not actively involved.