I am searching for information/documentation/tools from open source in re
1) mitigate risk of network vulnerabilities
Mind telling us what you have in mind? Are you talking redundancy, out of band communication or just properly configuring, hardening and shielding hosts and networks? (The last one should always be done, no matter what).
2) detect anomalies,
3) to analysis network activity,
4) network forensic monitor
Check out the LQ FAQ: Security references
, post 3.
Any advice on URL or pointer would be much appreciated.
Freshmeat is cool if you're hunting for SW, but it doesn't teach you security basics. Read some, experiment, ask some more before you blindly deploy the first thing you got compiled I'd say.