Filtration camps or filtration points (the official name) were used by the Russian federal forces for their mass internment centers during the First Chechen Wars in 1994-1996 and then again during the Second Chechen War between 1999 and 2003.
The original "filtration camp" system, run by the Soviet Union's NKVD, was established in 1945 for Soviet citizens that have been previously held prisoner by Germans during World War II. More than four million former Soviet POWs and civilian internees (mostly former forced laborers for Germany) went through hundreds of such "filtration camps" (sometimes also referred to as "control-filtration camps", "screening-filtration camps" or "verification-filtration camps") during the late 1940s.
The term "filtration point" re-appeared during the First Chechen War as name of the facilities illegally created for the purpose of holding the persons detained by the federal forces in the course of an operation "to restore constitutional order" on the territory of Chechen Republic in 1994-1996. During the Second Chechen War, beginning in 1999, some of the "filtration" facilities got legitimate status of investigative isolators (SIZO) subordinated to the Ministry of Justice and temporary detention isolators (IVS) subordinated to the Interior Ministry, but with an unclear legal status and no apparent basis in the criminal code of the Russian Federation.
According to the Russian human rights group Memorial, "by the most modest estimations", the overall number of those having passed through the established and ad hoc "filtration points" reaches at least 200,000 people (out of Chechnya's population of less than one million), of whom "practically all" have been subjected to beatings and torture, and some were summarily executed. According to Memorial, the purpose of the "filtration" system in Chechnya, besides being part of the general state terror system for suppression and intimidation of the population, was to create a network of informers through the enforced recruitation, and was characterised by its non-selectivity, that is by arbitrary arrests and mass detentions of innocent people.