Hi, I have a few questions.

Ok, I have a linksys router with a built in firewall and when I check the logs I typically see this:

2005-03-27 11:13:30 @in 4982/TCP from 2xx.4x.2xx.xx:80 to 192.168.1.101:4982 Invalid TCP packet received, dropping packet
How exactly does the router know which packets are invalid and which aren't? What constitutes an invalid packet? Does anyone know the rule list (I guess that's what it's called) that the linksys router is using to determine which are packets are suitable and which are not?

Any info is welcome. Please excuse my ignorance.