The present invention relates to a method for producing biocidal, porous particles of a cross-linked polymer, and to the porous particles that can be produced according to the method of the invention. The invention further relates to porous particles of an amino-group-containing polymer (polyamine) having a relatively low swelling factor. The porous particles according to the invention are used to remove biological contaminants from water and to bind metal-containing ions from solutions. The present invention further relates to a filter cartridge which contains the porous cross-linked polymer particles according to the invention.