C# library and sample GUI to interface into Google Safe Browsing API http://code.google.com/apis/safebrowsing/ The API allows checking of urls to determine if they are on a blacklist for malware or phishing attacks.
The library uses a provider model for the data store used to hold the blacklists, included in the source is a Sqlite provider that is used by the GUI. However it’s easy to write a new provider for MS Sql, Oracle or even an xml file.
To use the API you need to get a key from Google, you can get one from here http://code.google.com/apis/safebrowsing/key_signup.html
Then simply update app.config with your key.
Using the C# library you could implement a solution to check blog comments for malware or phishing attacks.
One thing to bear in mind is that at the moment the phishing detection rate is low, see my post here http://groups.google.com/group/google-safe-browsing-api/browse_thread/thread/22bfe22fc8ac05e0
At the moment I’m unable to implement the HMAC on the returned blacklist update, I don’t seem to be able to generate the correct HMAC to validate this, if you know the answer get in contact. This doesn’t affect the operation of the library adversely.
Update 12/2007
Keyvan Nayyeri has just released an alternative Google Safe Browsing Library for .NET, you can read more about it over at his blog.
Download
There are two downloads available, both released under a BSD license
Library, GUI and Sqlite provider (with semi populated data)
Separate library containing Mbunit tests for library