Anti-Spam Protection

As a Forum Member I don't like to receive spam PMs or see spam topics/posts so that I'm not distracted from main content

Ideas

• Restrict user from sending PMs for some time after registration
• Restrict user from sending PMs until he leaves N posts at forum
• Restrict the frequency of leaving posts/PMs. E.g. user isn't allowed to leave 2 PMs in 5 secs interval. After 5 secs passed if he leaves another PM in a minute, then he's not allowed to send 3d message for 25 secs. If he leaves 3d message in 2mins, then he'll be able to send his 4th message only after 125 secs. This algorithm is not precisely defined, just a brainstorm idea.
• Allow to send PMs only to a particular group (admins) until ...
• Button Mark As Spam - admin gets a notification, after N of such marks user can be automatically banned.
• Calculate the similarity of the PMs sent by user and if they are too similar, restrict his activity and send a message to admin.
• Moderate first N messages. If moderator didn't react during N hours, the message gets delivered to the receiver.

Analysis Results

• JavaTalks doesn't seem to be hacked in an automated manner
• Most spammers leave 1-2 messages. The actual numbers:
  • Min. : 1.00
  • 1st Qu.: 1.00
  • Median : 2.00
  • Mean : 43.22
  • 3rd Qu.: 13.00
  • Max. :2760.00

Analysis

• According to spammers-activity-vs-releases features (including spam-protection) do not impact the spam rate and the activity is random and unpredictable.
• When spammers start to leave messages:
  • 1.68% after less than 30mins
  • 3.36% between 30mins & 2hrs
  • 16.8% between 2hrs & 1day
  • 78.15% after 1 day passed. Thus doesn't seem like a bot behaviour.