Failed checksum from "IP"
 

I have a Linux Debian 3.0 server. There has been a continuous message that pops up that says:

IP_MASQ:reverse ICMP: failed checksum from 217.127.10.23

Sometimes I have many of these in a row with the same IP address.

So what is this person/computer doing and is there a way I can protect myself.

Thanks

So what is this person/computer doing and is there a way I can protect myself.
Message is to notify (level "informational" not a critical error) you the kernel found a bad packet checksum. Since the kernel already intercepted and dropped it there's nothing you need to do or worry about.

Dig It!
 

Glad to hear it.

What is this person trying to do?

The reason I ask is because I see the same IP address from a weeks ago come up again and again. So to me this is someone who is coming back to my box and messing with it. Can I find out who this person is? Can I mask myself so they cannot see me? Can I send his computer a power serge so it catches on fire and burns his house down? :)

Thanks

The first thing to realise is the most common cause for these type of messages is bad network conditions not malicious activity. Then realise the kernel ALREADY dropped the bad packet before you see the logged message, so the packet wasn't used, no harm done.

If you want to investigate, you'll need to find out if you or anything on your LAN has dealings with this IP address, like if you try to access services overthere, or if you provide services or play games. Easiest way would be to set up your firewall with full in/outbound logging using LOG target rules and take it from there.