CleanTalk .NET Spam Protection & C# Bot Filter — Easy Anti-Spam API Wrapper

CleanTalk C# Anti-Spam

Invisible spam protection for C# web apps — no CAPTCHA, no puzzles.
CleanTalk offers a lightweight spam filter and form protection middleware that works in the background, allowing developers to focus on features — not spam fixes.

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Actual API documentation

• check_message - Check IPs, Emails and messages for spam activity
• check_newuser - Check registrations of new users
• spam_check - This method should be used for bulk checks of IP, Email for spam activity
• ip_info - method returns a 2-letter country code (US, UK, CN, etc.) for an IP address

How does the API stop spam?

The API uses several simple tests to stop spammers.

• Spambot signatures.
• Blacklist checks by Email, IP, website domain names.
• Javascript availability.
• Comment submit time.
• Relevance test for the comment.

How does the API work?

API sends the comment's text and several previous approved comments to the server. The server evaluates the relevance of the comment's text on the topic, tests for spam and finally provides a solution - to publish or to put in manual moderation queue of comments. If a comment is placed in manual moderation queue, the plugin adds a rejection explanation to the text of the comment.

Requirements

• .Net Framework v4.8
• CleanTalk account https://cleantalk.org/register?product=anti-spam

Websites that trust CleanTalk!

Integration Example (ASP.NET Middleware)

publicvoidConfigure(IApplicationBuilderapp){app.UseCleanTalk(spamCheckOptions =>{spamCheckOptions.AuthKey="YOUR_KEY";});app.UseEndpoints(endpoints =>{endpoints.MapPost("/contact",async context =>{varct=context.RequestServices.GetRequiredService<ICleanTalkService>();varisSpam=awaitct.CheckMessageAsync(newSpamCheckRequest{Message=awaitnewStreamReader(context.Request.Body).ReadToEndAsync(),SenderIp=context.Connection.RemoteIpAddress.ToString(),SenderEmail="user@example.com"});if(isSpam)context.Response.StatusCode=403;elseawaitcontext.Response.WriteAsync("Thanks!");});});}Thisexample demonstrates how to protect a simple POST form usingCleanTalk’smiddleware.Itworks invisibly — no CAPTCHA required.
## SPAM test examples
### Usage of check_message method for text comment verify
```c#
publicconststringAuthKey="auth key";//...varreq1=newCleantalkRequest(AuthKey){Message="This is a great storm!",SenderInfo=newSenderInfo{Refferrer="https://www.bbc.co.uk/sport",UserAgent="Opera/9.80 (Windows NT 6.1; WOW64) Presto/2.12.388 Version/12.12"},SenderIp="91.207.4.192",SenderEmail="keanu8dh@gmail.com",SenderNickname="Mike",EventToken="f32f32f32f32f32f32f32f32f32f32a2",/// To get this param:/// 1. add a script to the web-page: <script src="https://fd.cleantalk.org/ct-bot-detector-wrapper.js" id="ct_bot_detector-js"></script>/// 2. parse the newly added hidden input on the web form, the name atrribute of input is "ct_bot_detector_event_token" /// @var stringSubmitTime=15};varres1=_cleantalk.CheckMessage(req1);

API returns response object:

• allow (0|1) - allow to publish or not, in other words spam or ham.
• comment (string) - server comment for requests.
• id (string MD5 HEX hash) - unique request idenifier.
• errno (int) - error number. errno will be 0 if request is successful.
• errtstr (string) - comment explaining the error. errstr will be null if request is successful.

Usage of spam_check method for bulk parameters

publicconststringSpamCheckAuthKey="spam_check auth key";//...varreq1=newSpamCheckRequest(SpamCheckAuthKey){data="stop_email@example.com,10.0.0.1,10.0.0.2"};varres1=_cleantalk.SpamCheck(req1);

Result:

{
"data":
{
"stop_email@example.com":{
"appears":true,
"disposable_email":false,
"sha256":"6d42ca0235d72b01a2b086ad53b5cfac24b5a444847fad70250e042d7ca8bf59",
"spam_rate":0,
"submitted":"2023-09-06 07:20:49",
"updated":"2023-09-06 07:20:49"
},
"10.0.0.1":{
"domains_count":1510,
"frequency":2,
"network_type":"hosting",
"sha256":"f5047344122f0dee9974ba6761e61c6b8649e1f3968d13a635ebbf7be53a3a0d",
"spam_rate":0,
"submitted":"2020-06-19 09:57:46",
"updated":"2023-11-01 18:58:11"
},
"10.0.0.2":{
"domains_count":35,
"frequency":1,
"network_type":"hosting",
"sha256":"cb5f37b4762871e6bbeccee663cb332438340c469160c634566ecc7c7e01009f",
"spam_rate":0,
"submitted":"2022-01-18 19:58:09",
"updated":"2023-07-19 18:58:13"
}
}
}

Usage of ip_info method for detecting county 2-letter code

publicconststringAuthKey="auth key";//...varres1=_cleantalk.IpInfoCheck(AuthKey,"8.8.8.8","213.239.245.253","109.191.240.212");

Result:

{
"data":
{
"8.8.8.8":{"country_code":"US","country_name":"United States"},
"213.239.245.253":{"country_code":"DE","country_name":"Germany"},
"109.191.240.212":{"country_code":"RU","country_name":"Russian Federation"}
}
}