Testing ------- Install package: c-icap libc-icap-mod-clamav clamav Add Include srv_clamav.conf to /etc/c-icap/c-icap.conf . Basic functionality testing: The package c-icap contains a c-icap-client command line tool which can be used for the first test: icap-client c-icap-client -f /bin/ls -s "srv_clamav?allow204=on&force=on&sizelimit=off&mode=simple" should report "No modification needed (Allow 204 response)". c-icap-client -f eicar.com.txt -s "srv_clamav?allow204=on&force=on&sizelimit=off&mode=simple" should report that virus is found (Eicar-Test-Signature). Test c-icap with squid3: squid.conf: icap_enable on icap_preview_size 1024 icap_send_client_ip on icap_client_username_header X-Authenticated-User icap_service service_req reqmod_precache bypass=0 icap://127.0.0.1:1344/antivirus_module icap_service service_resp respmod_precache bypass=0 icap://127.0.0.1:1344/antivirus_module adaptation_access service_req allow all adaptation_access service_resp allow all Set http(s)_proxy for squid, and check downloading e.g http://www.eicar.org/download/eicar.com.txt .