In the code below if I get into the if statement I can safely say my site is under attack. What information is it a good idea to log?
Any recommendations on actions that can be taken to minimize the damage at this point?

protected void btn_Search_Click(object sender, EventArgs e)
{
   if(tb_SearchBox.Text.Length > tb_SearchBox.MaxLength)
   {
      //What should i log?
      //What actions should I take?
   }
   //Otherwise search
}