I find 100s of these types of entries in my drupal log. It tries URLs like this below. It happens when there's very less traffic on our site. What is it trying to do? Is it a security threat? Can it cause any harm to our site & data? Can they be stopped?
https://example.com/civicrm/contribute/transact?reset=1%27%20AND%206876%20IN%20%28SELECT%20%28CHAR%28113%29%2BCHAR%28106%29%2BCHAR%2898%29%2BCHAR%28122%29%2BCHAR%28113%29%2B%28SELECT%20%28CASE%20WHEN%20%286876%3D6876%29%20THEN%20CHAR%2849%29%20ELSE%20CHAR%2848%29%20END%29%29%2BCHAR%28113%29%2BCHAR%28118%29%2BCHAR%28106%29%2BCHAR%28112%29%2BCHAR%28113%29%29%29%20AND%20%27KFmQ%27%3D%27KFmQ&id=10