How does Avast’s Web Shield differ from OpenDNS/GoogleDNS/ComodoDNS (mainly talking about the malware prevention parts)?
Thanks.
Chalk and Cheese.
They do different things OpenDNS replaces your ISP DNS server and if you use its dashboard feature you can also set it up to block certain categories of web site, e.g. adult, social networking, etc.
I have never user the other two so I can’t say what their function is, but my guess is they try to emulate OpenDNS.
The web shield physically scans port 80 HTTP Traffic for malware and the three you mentioned don’t do that, certainly OpenDNS doesn’t. See image extract from the avast help file, Real Time Shields, Overview.
Can you translate this for your friends across the pond? 
EDIT: Never mind. I should have just tried a search first. 
Comodo and Google DNS function the same as OpenDNS, albeit with slightly different landing pages if you hit a bad or non-existent URL. I’ve tried all three, but have stayed with OpenDNS.
yeah, david’s answer was still appropriate, as you cannot compare, even in terms of security potential, apples and apes ;D …, ie avast web shield and dns servers
Sorry, I should have confirmed it before posting.
My bad, I meant the Network Shield.
It also blocks sites to known malicious sites.
Same answer, they do different things.
The network shields list of known malicious sites also gains information from the stats on detections by the web shield, so if there are a rash of alerts on a site over time that could result in it being added to the malicious sites list.
This has happened to a number of sites in the past which have been hacked, this type of attack from hacked sites is becoming more and more frequent and is an area that OpenDNS, etc. do nothing about as the site is still legit in their eyes.
OpenDNS, etc. don’t monitor known attack ports and block exploit attempts if your firewall fails to do so (seem in many forum topics).