Generic Settings for CONNLIMIT and PORTFLOOD to Stop attack

[aditya36955]

Dear Team

i have vps with Xeon 4 cores and 3GB ram with Shared hosting environment

Some users giving lot of load to server with many https connections .. some are trying Dos attacks on server

I need prevent all these

Any one please suggest Generic settings for CONNLIMIT and PORTFLOOD to Stop Dos and some other attacks ..

Please suggest these settings ..

thamks

[aditya36955]

and also i am receiving some mails from root as
This message is to alert you that the username frighta1_wp648 has exceeded their MySQL connection limit. Please view the details below.

User: frighta1_wp648
MySQL Connection Limit:
Current MySQL Connections: 41

How to prevent these my sql connections ? and please suggest above limits