[Techtalk] Personal firewalls: helpful?

[Dan]

I've heard of Windows users running personal firewalls (i.e.,
implemented in software). I don't have to worry about that because I
don't run Windows, but I do wonder whether these personal firewalls do
any good. Obviously they're not as good as a dedicated machine, but I
assume they still provide some protection.

Does anyone know what kind of attacks personal firewalls protect against
(and what kind of attacks they don't)?

-- 
Dogs have owners; cats have staff.