There are various reasons why CSF firewall may make your WHM / server slow.
Here are some personal tips from me.
- Change your default SSH Port from 22 to something else. It will prevent (although temporarily) malicious bots from scanning your server, and adding extra load to your firewall.
- Edit your CSF firewall configuration, and change these configuration :
- CC_LOOKUPS : 0
This will disable IP country lookup. Imagine your firewall blocking hundreds of IP each second, and doing additional country lookup for each IP. - LF_EMAIL_ALERT : OFF
- LT_EMAIL_ALERT : OFF
- CT_EMAIL_ALERT : OFF
- PS_EMAIL_ALERT : OFF
*_EMAIL_ALERT things will disable sending email from your server to your e-mail address which will add extra work for your server if your server is scanned by hundreds of IP each second.
- CC_LOOKUPS : 0
If you have other tips for improving CSF speed, please comment below 🙂