def open

 NIPS/NIDS
https://www.snort.org/
http://suricata-ids.org/
http://sagan.quadrantsec.com/
HIDS/HIPS
http://www.ossec.net/
Sandbox:
http://www.cuckoosandbox.org/
http://habrahabr.ru/post/234467/
WAF
https://www.modsecurity.org/
https://github.com/nbs-system/naxsi
DDOS
https://github.com/nbs-system/naxsi
http://kyprizel.github.io/testcookie-nginx-module/
SIEM:
http://www.alienvault.com/open-threat-exchange
https://www.prelude-ids.org/
AV
http://www.clamav.net/index.html
AntiSpam
http://sourceforge.net/projects/assp/
Encryption
https://github.com/FauxFaux/truecrypt
https://www.gnupg.org/
Honeypot
http://threatstream.github.io/mhn/
http://www.honeyd.org/