Hello,
does it make sense to activate the Network Shield of Avast if Comodo Personal Firewall is already running?
It won’t hurt or use resources.
But, indeed, if your operational system is updated and you have a good firewall, no need for NetShield.
I agree to that, I haven’t thought of turning off the Network Shield in avast!, I just ran Comodo Firewall and avast! (with all providers running except Outlook/Exchange) without problems.
And since the NS is not using resources, I will continue doing the same thing 
Hmm. not quite satisfied with the answers.
The simple question is: Does the Avast Network Shield detect the same threats as Comodo does, or does it add additional security measures?
Well, how can we know? [what Comodo detects] - we are not really familiar with all Comodo internals or detections.
I can post ‘technical’ info about it:
Network Shield is a protection against known Internet worms/attacks. It analyses all network traffic and scans it for malicious contents. It can be also taken as a lightweight firewall (or more precisely, an IDS (Intrusion Detection System).
Network Shield protects you from internet worms that spread themselves via various security holes in your system. Typicaly these kind of viruses don’t infect files but instead they attack running processes on your PC (either Windows components or some server programs like SQL Server, IIS etc.). These kind of attacks are not easily catched by ordinary antivirus during file or mail scanning. It is not a duplicate work with Standard Shield.
It scans incomming packets which are sent to particular ports (like 445, 135, 5554, … where an attacker can exploit your computer; it’s the protection against blaster/sasser/… worms). The network shield does not block or slow down other network traffic on other ports (NetShield ignores them).
Thanks for the explanation Tech, I was wondering what net shield really did.
Is there a complete List of what worms are detected by Network Shield?
I can only contribute with part of the list:
Win32.CodeRed, Win32.SQLSlammer, Win32.Blaster, in32.Welchia (Nachi) and Win32.Sasser.
Maybe other users (or Alwil team) could do the rest ;D
Thanks Tech for the part of the list.
Hopefully avast support will post the complete list here.
As far as I have checked comodo, it does not scan for the worm threats. So I additionally installed the network shield as it does not slow down the system and also does not use an additional service.