If it directly boots burned discs without requiring a special MC, then it has a hardware modchip.
I din't buy my ps2 from Sony, i got it from a grey market where they sell ps2 which are already modded. Now i believe there is something called as soft modd and hard modd...and iam not sure mine is which one..
I do not use online games myself, so I am no expert on how various such games respond to modchip use.
Yes, i think my friend who also has a modded ps2 slim like me...tried goin online and cud not do it..though he setup his internet connection. DNS server and all through his wi fi ..widout ny NAD disc.
As u mentioned most games have anti-mod and and ant-cheat protection methods, will it be of any help if i try n look for NAD disc and try goin online wid it...Do u happen to know any particular games which run online on modded ps2;s?