Sysadmin DDOS attack, how to detect and prevent

First become familiar with tools and monitoring below

CPU load optimal is 1.0 per cpu thread so 8 cpu thread normal = 8x1 = 8.0. 16 cpu server normal is 16x1 = 16.0

so cpu load of 8 for

• 2 cpu server = 8/2 = 4.0 load average
• 4 cpu server = 8/4 = 2.0 load average
• 8 cpu server = 8/8 = 1.0 load average

When you type top command, hit number 1 to break down per cpu stats

Centmin Mod is provided as is, so troubleshooting load issues is left to end user to do. However, there's many linux tools and scripts that can help you figure out what was causing the load and slowness issues and when.

If you're providing info on this forum, more info might be helpful

1. What version of Centmin Mod ? .08 stable or .09 beta ? If .09 beta when was it installed and when was last time you updated ?
2. What's your VPS/Server hardware specifications ? cpu type ? memory available ? disk space ?
3. Who's your web host ? Different hosts have different limits for server resource usage and some are more restrictive that others so it could just be their resource usage policy you tripped which may or may not be restrictive. If restrictive, then real solution would be finding a better web host. If not restrictive, then it's finding out what caused high cpu load.

Tools and commands you will want to read up on and learn for basic system admin tasks and troubleshooting.

• 20 Command Line Tools to Monitor Linux Performance
• 13 Linux Performance Monitoring Tools - Part 2
• 80 Linux Monitoring Tools for SysAdmins - Server Density Blog
• Amazing ! 25 Linux Performance Monitoring Tools
• 20 Linux System Monitoring Tools Every SysAdmin Should Know
• My mysqlmymonlite.sh script can help with that mysqlmymonlite.sh Addon | Centmin Mod Community README text file has instructions for setting up a cronjob to email you reports i.e. every 10/15min or every hour.

Notes:

• Centmin Mod already installed Glances tool. It can be invoked from SSH command glances or top2. Official Glances site at nicolargo.github.io/glances/ and documentation here.