What exactly need to be done and how to proceed with the Malicious attacks (brute force , DDos , Botnet etc) on network.
If one has to perform a manual intervention when an attack is occurring then the battle to defend the network is all but lost.
To defend a network attack one must be on-your-toes. Read Cisco Guide to Harden Cisco IOS Devices.
IPS/IDS are good tools ... only if it's properly configured, properly maintained, and (very) regularly monitored.
